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return OleDbDataReader from static functionI want to return OleDbDataReader from a static function, So I will have DB interface for my Entire project, Is it possible? How do I close the connection ?????? Thank you Sharon ///////////////////////////////////////////////////////////// //Example of use : ///////////////////////////////////////////////////////////// OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, ContactName, FROM Customers") While (reader.Read()){ System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : " + reader("ContactName").ToString() + "<br>") /////////////////////////////////////////////////////////////} //select function : ///////////////////////////////////////////////////////////// Public static OleDbDataReader Select (string selectString) { 'Use a string variable to hold the ConnectionString property. String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ "Data Source=C:\\Program Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" OleDbConnection cn = New OleDbConnection(connectString) 'Open the connection. cn.Open() 'Use a variable to hold the SQL statement. String As String = OleDbCommand cmd = New OleDbCommand(selectString, cn) Return cmd.ExecuteReader() 'Close the reader and the related connection. // reader.Close() //?????????????????????????????????????????????????? cn.Close() } If you are returning the reader, you have to wait for the user to close the
reader. In order for closing the reader to close the connection, you have to pass in CommandBehavior.CloseConnection into ExecuteReader. However, this still means the user of this function has to remember to close it. None of the code after the Return statement in your function will execute, the 'Return' statement immediately exits the function. In general, the rule of thumb is don't do this. Return datatables. Show quote "Sharon" <Sharon***@hotmail.com> wrote in message news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... > Hi all > I want to return OleDbDataReader from a static function, > So I will have DB interface for my Entire project, > Is it possible? > How do I close the connection ?????? > > Thank you > Sharon > > ///////////////////////////////////////////////////////////// > //Example of use : > ///////////////////////////////////////////////////////////// > OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, ContactName, > FROM Customers") > While (reader.Read()){ > > System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : " > + reader("ContactName").ToString() + "<br>") > } > > ///////////////////////////////////////////////////////////// > //select function : > ///////////////////////////////////////////////////////////// > Public static OleDbDataReader Select (string selectString) > { > 'Use a string variable to hold the ConnectionString property. > String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ > "Data Source=C:\\Program > Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" > > OleDbConnection cn = New OleDbConnection(connectString) > > 'Open the connection. > cn.Open() > > 'Use a variable to hold the SQL statement. > String As String = > > OleDbCommand cmd = New OleDbCommand(selectString, cn) > > Return cmd.ExecuteReader() > > 'Close the reader and the related connection. > // reader.Close() > //?????????????????????????????????????????????????? > cn.Close() > > } > > Hi marina
Thank you for your answer so it will be like : >> OleDbCommand cmd = New OleDbCommand(selectString, cn) What is the differences between datatables and OleDbDataReader>> datatable mydt = cmd.doSomething(); >> >> 'Close the connection. >> cn.Close() >> return mydt Thank you again Sharon Show quote "Marina" <someone@nospam.com> wrote in message news:O5UywQKNFHA.2384@tk2msftngp13.phx.gbl... > If you are returning the reader, you have to wait for the user to close > the reader. In order for closing the reader to close the connection, you > have to pass in CommandBehavior.CloseConnection into ExecuteReader. > > However, this still means the user of this function has to remember to > close it. > > None of the code after the Return statement in your function will execute, > the 'Return' statement immediately exits the function. > > In general, the rule of thumb is don't do this. Return datatables. > > "Sharon" <Sharon***@hotmail.com> wrote in message > news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >> Hi all >> I want to return OleDbDataReader from a static function, >> So I will have DB interface for my Entire project, >> Is it possible? >> How do I close the connection ?????? >> >> Thank you >> Sharon >> >> ///////////////////////////////////////////////////////////// >> //Example of use : >> ///////////////////////////////////////////////////////////// >> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, ContactName, >> FROM Customers") >> While (reader.Read()){ >> >> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : >> " + reader("ContactName").ToString() + "<br>") >> } >> >> ///////////////////////////////////////////////////////////// >> //select function : >> ///////////////////////////////////////////////////////////// >> Public static OleDbDataReader Select (string selectString) >> { >> 'Use a string variable to hold the ConnectionString property. >> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >> "Data Source=C:\\Program >> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >> >> OleDbConnection cn = New OleDbConnection(connectString) >> >> 'Open the connection. >> cn.Open() >> >> 'Use a variable to hold the SQL statement. >> String As String = >> >> OleDbCommand cmd = New OleDbCommand(selectString, cn) >> >> Return cmd.ExecuteReader() >> >> 'Close the reader and the related connection. >> // reader.Close() >> //?????????????????????????????????????????????????? >> cn.Close() >> >> } >> >> > > Sharon, DataTable is a disconnected data cache. In your case, if the data is
small, it make sense to cache it and then pass it to the user. HTH, Sushil. Show quote "Sharon" <Sharon***@hotmail.com> wrote in message news:%23z5BdWKNFHA.3900@TK2MSFTNGP10.phx.gbl... > Hi marina > > > > Thank you for your answer > > so it will be like : > >>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>> datatable mydt = cmd.doSomething(); >>> >>> 'Close the connection. >>> cn.Close() >>> return mydt > > > > What is the differences between datatables and OleDbDataReader > > > > Thank you again > > Sharon > > > > "Marina" <someone@nospam.com> wrote in message > news:O5UywQKNFHA.2384@tk2msftngp13.phx.gbl... >> If you are returning the reader, you have to wait for the user to close >> the reader. In order for closing the reader to close the connection, you >> have to pass in CommandBehavior.CloseConnection into ExecuteReader. >> >> However, this still means the user of this function has to remember to >> close it. >> >> None of the code after the Return statement in your function will >> execute, the 'Return' statement immediately exits the function. >> >> In general, the rule of thumb is don't do this. Return datatables. >> >> "Sharon" <Sharon***@hotmail.com> wrote in message >> news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>> Hi all >>> I want to return OleDbDataReader from a static function, >>> So I will have DB interface for my Entire project, >>> Is it possible? >>> How do I close the connection ?????? >>> >>> Thank you >>> Sharon >>> >>> ///////////////////////////////////////////////////////////// >>> //Example of use : >>> ///////////////////////////////////////////////////////////// >>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>> ContactName, FROM Customers") >>> While (reader.Read()){ >>> >>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : >>> " + reader("ContactName").ToString() + "<br>") >>> } >>> >>> ///////////////////////////////////////////////////////////// >>> //select function : >>> ///////////////////////////////////////////////////////////// >>> Public static OleDbDataReader Select (string selectString) >>> { >>> 'Use a string variable to hold the ConnectionString property. >>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>> "Data Source=C:\\Program >>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>> >>> OleDbConnection cn = New OleDbConnection(connectString) >>> >>> 'Open the connection. >>> cn.Open() >>> >>> 'Use a variable to hold the SQL statement. >>> String As String = >>> >>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>> >>> Return cmd.ExecuteReader() >>> >>> 'Close the reader and the related connection. >>> // reader.Close() >>> //?????????????????????????????????????????????????? >>> cn.Close() >>> >>> } >>> >>> >> >> > > Hi Marina,
Why do you say not to return a DataReader. If she uses the CommandBehavior.CloseConnection, I can see no reason not to use it. What am I missing? TIA John Show quote On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> wrote: >If you are returning the reader, you have to wait for the user to close the >reader. In order for closing the reader to close the connection, you have to >pass in CommandBehavior.CloseConnection into ExecuteReader. > >However, this still means the user of this function has to remember to close >it. > >None of the code after the Return statement in your function will execute, >the 'Return' statement immediately exits the function. > >In general, the rule of thumb is don't do this. Return datatables. > >"Sharon" <Sharon***@hotmail.com> wrote in message >news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >> Hi all >> I want to return OleDbDataReader from a static function, >> So I will have DB interface for my Entire project, >> Is it possible? >> How do I close the connection ?????? >> >> Thank you >> Sharon >> >> ///////////////////////////////////////////////////////////// >> //Example of use : >> ///////////////////////////////////////////////////////////// >> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, ContactName, >> FROM Customers") >> While (reader.Read()){ >> >> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : " >> + reader("ContactName").ToString() + "<br>") >> } >> >> ///////////////////////////////////////////////////////////// >> //select function : >> ///////////////////////////////////////////////////////////// >> Public static OleDbDataReader Select (string selectString) >> { >> 'Use a string variable to hold the ConnectionString property. >> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >> "Data Source=C:\\Program >> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >> >> OleDbConnection cn = New OleDbConnection(connectString) >> >> 'Open the connection. >> cn.Open() >> >> 'Use a variable to hold the SQL statement. >> String As String = >> >> OleDbCommand cmd = New OleDbCommand(selectString, cn) >> >> Return cmd.ExecuteReader() >> >> 'Close the reader and the related connection. >> // reader.Close() >> //?????????????????????????????????????????????????? >> cn.Close() >> >> } >> >> > Missing the fact that you are relying on the consumer of the function to
remember to close the reader when they are done. Someone forgets to close it in one place, and before you know it you are tracking down a connection pool out of connections leak in your program. You would be surprised how often that happens. Show quote "J L" <j***@marymonte.com> wrote in message news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... > Hi Marina, > Why do you say not to return a DataReader. If she uses the > CommandBehavior.CloseConnection, I can see no reason not to use it. > What am I missing? > > TIA > John > > On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> > wrote: > >>If you are returning the reader, you have to wait for the user to close >>the >>reader. In order for closing the reader to close the connection, you have >>to >>pass in CommandBehavior.CloseConnection into ExecuteReader. >> >>However, this still means the user of this function has to remember to >>close >>it. >> >>None of the code after the Return statement in your function will execute, >>the 'Return' statement immediately exits the function. >> >>In general, the rule of thumb is don't do this. Return datatables. >> >>"Sharon" <Sharon***@hotmail.com> wrote in message >>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>> Hi all >>> I want to return OleDbDataReader from a static function, >>> So I will have DB interface for my Entire project, >>> Is it possible? >>> How do I close the connection ?????? >>> >>> Thank you >>> Sharon >>> >>> ///////////////////////////////////////////////////////////// >>> //Example of use : >>> ///////////////////////////////////////////////////////////// >>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>> ContactName, >>> FROM Customers") >>> While (reader.Read()){ >>> >>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : >>> " >>> + reader("ContactName").ToString() + "<br>") >>> } >>> >>> ///////////////////////////////////////////////////////////// >>> //select function : >>> ///////////////////////////////////////////////////////////// >>> Public static OleDbDataReader Select (string selectString) >>> { >>> 'Use a string variable to hold the ConnectionString property. >>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>> "Data Source=C:\\Program >>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>> >>> OleDbConnection cn = New OleDbConnection(connectString) >>> >>> 'Open the connection. >>> cn.Open() >>> >>> 'Use a variable to hold the SQL statement. >>> String As String = >>> >>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>> >>> Return cmd.ExecuteReader() >>> >>> 'Close the reader and the related connection. >>> // reader.Close() >>> //?????????????????????????????????????????????????? >>> cn.Close() >>> >>> } >>> >>> >> > Ahhh...very good point. Thanks.
John Show quote On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> wrote: >Missing the fact that you are relying on the consumer of the function to >remember to close the reader when they are done. > >Someone forgets to close it in one place, and before you know it you are >tracking down a connection pool out of connections leak in your program. You >would be surprised how often that happens. > >"J L" <j***@marymonte.com> wrote in message >news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >> Hi Marina, >> Why do you say not to return a DataReader. If she uses the >> CommandBehavior.CloseConnection, I can see no reason not to use it. >> What am I missing? >> >> TIA >> John >> >> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >> wrote: >> >>>If you are returning the reader, you have to wait for the user to close >>>the >>>reader. In order for closing the reader to close the connection, you have >>>to >>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>> >>>However, this still means the user of this function has to remember to >>>close >>>it. >>> >>>None of the code after the Return statement in your function will execute, >>>the 'Return' statement immediately exits the function. >>> >>>In general, the rule of thumb is don't do this. Return datatables. >>> >>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>> Hi all >>>> I want to return OleDbDataReader from a static function, >>>> So I will have DB interface for my Entire project, >>>> Is it possible? >>>> How do I close the connection ?????? >>>> >>>> Thank you >>>> Sharon >>>> >>>> ///////////////////////////////////////////////////////////// >>>> //Example of use : >>>> ///////////////////////////////////////////////////////////// >>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>> ContactName, >>>> FROM Customers") >>>> While (reader.Read()){ >>>> >>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : >>>> " >>>> + reader("ContactName").ToString() + "<br>") >>>> } >>>> >>>> ///////////////////////////////////////////////////////////// >>>> //select function : >>>> ///////////////////////////////////////////////////////////// >>>> Public static OleDbDataReader Select (string selectString) >>>> { >>>> 'Use a string variable to hold the ConnectionString property. >>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>> "Data Source=C:\\Program >>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>> >>>> OleDbConnection cn = New OleDbConnection(connectString) >>>> >>>> 'Open the connection. >>>> cn.Open() >>>> >>>> 'Use a variable to hold the SQL statement. >>>> String As String = >>>> >>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>> >>>> Return cmd.ExecuteReader() >>>> >>>> 'Close the reader and the related connection. >>>> // reader.Close() >>>> //?????????????????????????????????????????????????? >>>> cn.Close() >>>> >>>> } >>>> >>>> >>> >> > One more question....if the DataReader goes out of scope before it is
closed....what happens? John Show quote On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> wrote: >Missing the fact that you are relying on the consumer of the function to >remember to close the reader when they are done. > >Someone forgets to close it in one place, and before you know it you are >tracking down a connection pool out of connections leak in your program. You >would be surprised how often that happens. > >"J L" <j***@marymonte.com> wrote in message >news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >> Hi Marina, >> Why do you say not to return a DataReader. If she uses the >> CommandBehavior.CloseConnection, I can see no reason not to use it. >> What am I missing? >> >> TIA >> John >> >> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >> wrote: >> >>>If you are returning the reader, you have to wait for the user to close >>>the >>>reader. In order for closing the reader to close the connection, you have >>>to >>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>> >>>However, this still means the user of this function has to remember to >>>close >>>it. >>> >>>None of the code after the Return statement in your function will execute, >>>the 'Return' statement immediately exits the function. >>> >>>In general, the rule of thumb is don't do this. Return datatables. >>> >>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>> Hi all >>>> I want to return OleDbDataReader from a static function, >>>> So I will have DB interface for my Entire project, >>>> Is it possible? >>>> How do I close the connection ?????? >>>> >>>> Thank you >>>> Sharon >>>> >>>> ///////////////////////////////////////////////////////////// >>>> //Example of use : >>>> ///////////////////////////////////////////////////////////// >>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>> ContactName, >>>> FROM Customers") >>>> While (reader.Read()){ >>>> >>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " : >>>> " >>>> + reader("ContactName").ToString() + "<br>") >>>> } >>>> >>>> ///////////////////////////////////////////////////////////// >>>> //select function : >>>> ///////////////////////////////////////////////////////////// >>>> Public static OleDbDataReader Select (string selectString) >>>> { >>>> 'Use a string variable to hold the ConnectionString property. >>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>> "Data Source=C:\\Program >>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>> >>>> OleDbConnection cn = New OleDbConnection(connectString) >>>> >>>> 'Open the connection. >>>> cn.Open() >>>> >>>> 'Use a variable to hold the SQL statement. >>>> String As String = >>>> >>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>> >>>> Return cmd.ExecuteReader() >>>> >>>> 'Close the reader and the related connection. >>>> // reader.Close() >>>> //?????????????????????????????????????????????????? >>>> cn.Close() >>>> >>>> } >>>> >>>> >>> >> > The connection stays open until the GC decides to collect it. In which case,
the Dispose would get called on the connection, which closes it. However, it is almost never the case that the GC does this before the pool is out of connections. So in essense you are guaranteed to get the connection pool is out of connections error. Show quote "J L" <j***@marymonte.com> wrote in message news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... > One more question....if the DataReader goes out of scope before it is > closed....what happens? > > John > > On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> > wrote: > >>Missing the fact that you are relying on the consumer of the function to >>remember to close the reader when they are done. >> >>Someone forgets to close it in one place, and before you know it you are >>tracking down a connection pool out of connections leak in your program. >>You >>would be surprised how often that happens. >> >>"J L" <j***@marymonte.com> wrote in message >>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>> Hi Marina, >>> Why do you say not to return a DataReader. If she uses the >>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>> What am I missing? >>> >>> TIA >>> John >>> >>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>> wrote: >>> >>>>If you are returning the reader, you have to wait for the user to close >>>>the >>>>reader. In order for closing the reader to close the connection, you >>>>have >>>>to >>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>> >>>>However, this still means the user of this function has to remember to >>>>close >>>>it. >>>> >>>>None of the code after the Return statement in your function will >>>>execute, >>>>the 'Return' statement immediately exits the function. >>>> >>>>In general, the rule of thumb is don't do this. Return datatables. >>>> >>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>> Hi all >>>>> I want to return OleDbDataReader from a static function, >>>>> So I will have DB interface for my Entire project, >>>>> Is it possible? >>>>> How do I close the connection ?????? >>>>> >>>>> Thank you >>>>> Sharon >>>>> >>>>> ///////////////////////////////////////////////////////////// >>>>> //Example of use : >>>>> ///////////////////////////////////////////////////////////// >>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>> ContactName, >>>>> FROM Customers") >>>>> While (reader.Read()){ >>>>> >>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " >>>>> : >>>>> " >>>>> + reader("ContactName").ToString() + "<br>") >>>>> } >>>>> >>>>> ///////////////////////////////////////////////////////////// >>>>> //select function : >>>>> ///////////////////////////////////////////////////////////// >>>>> Public static OleDbDataReader Select (string selectString) >>>>> { >>>>> 'Use a string variable to hold the ConnectionString property. >>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>> "Data Source=C:\\Program >>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>> >>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>> >>>>> 'Open the connection. >>>>> cn.Open() >>>>> >>>>> 'Use a variable to hold the SQL statement. >>>>> String As String = >>>>> >>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>> >>>>> Return cmd.ExecuteReader() >>>>> >>>>> 'Close the reader and the related connection. >>>>> // reader.Close() >>>>> //?????????????????????????????????????????????????? >>>>> cn.Close() >>>>> >>>>> } >>>>> >>>>> >>>> >>> >> > How about Dataset ?
Is this a cashed too? Show quote "Marina" <someone@nospam.com> wrote in message news:%23s8r7nTNFHA.940@TK2MSFTNGP09.phx.gbl... > The connection stays open until the GC decides to collect it. In which > case, the Dispose would get called on the connection, which closes it. > > However, it is almost never the case that the GC does this before the pool > is out of connections. So in essense you are guaranteed to get the > connection pool is out of connections error. > > "J L" <j***@marymonte.com> wrote in message > news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >> One more question....if the DataReader goes out of scope before it is >> closed....what happens? >> >> John >> >> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >> wrote: >> >>>Missing the fact that you are relying on the consumer of the function to >>>remember to close the reader when they are done. >>> >>>Someone forgets to close it in one place, and before you know it you are >>>tracking down a connection pool out of connections leak in your program. >>>You >>>would be surprised how often that happens. >>> >>>"J L" <j***@marymonte.com> wrote in message >>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>> Hi Marina, >>>> Why do you say not to return a DataReader. If she uses the >>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>> What am I missing? >>>> >>>> TIA >>>> John >>>> >>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>> wrote: >>>> >>>>>If you are returning the reader, you have to wait for the user to close >>>>>the >>>>>reader. In order for closing the reader to close the connection, you >>>>>have >>>>>to >>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>> >>>>>However, this still means the user of this function has to remember to >>>>>close >>>>>it. >>>>> >>>>>None of the code after the Return statement in your function will >>>>>execute, >>>>>the 'Return' statement immediately exits the function. >>>>> >>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>> >>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>> Hi all >>>>>> I want to return OleDbDataReader from a static function, >>>>>> So I will have DB interface for my Entire project, >>>>>> Is it possible? >>>>>> How do I close the connection ?????? >>>>>> >>>>>> Thank you >>>>>> Sharon >>>>>> >>>>>> ///////////////////////////////////////////////////////////// >>>>>> //Example of use : >>>>>> ///////////////////////////////////////////////////////////// >>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>> ContactName, >>>>>> FROM Customers") >>>>>> While (reader.Read()){ >>>>>> >>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + >>>>>> " : >>>>>> " >>>>>> + reader("ContactName").ToString() + "<br>") >>>>>> } >>>>>> >>>>>> ///////////////////////////////////////////////////////////// >>>>>> //select function : >>>>>> ///////////////////////////////////////////////////////////// >>>>>> Public static OleDbDataReader Select (string selectString) >>>>>> { >>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>> "Data Source=C:\\Program >>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>> >>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>> >>>>>> 'Open the connection. >>>>>> cn.Open() >>>>>> >>>>>> 'Use a variable to hold the SQL statement. >>>>>> String As String = >>>>>> >>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>> >>>>>> Return cmd.ExecuteReader() >>>>>> >>>>>> 'Close the reader and the related connection. >>>>>> // reader.Close() >>>>>> //?????????????????????????????????????????????????? >>>>>> cn.Close() >>>>>> >>>>>> } >>>>>> >>>>>> >>>>> >>>> >>> >> > > Nothing is getting cached. I am not sure what you mean. Caching was not at
all discussed in this thread. Show quote "Sharon" <Sharon***@hotmail.com> wrote in message news:eScAT9VNFHA.1172@TK2MSFTNGP12.phx.gbl... > How about Dataset ? > > Is this a cashed too? > > > > "Marina" <someone@nospam.com> wrote in message > news:%23s8r7nTNFHA.940@TK2MSFTNGP09.phx.gbl... >> The connection stays open until the GC decides to collect it. In which >> case, the Dispose would get called on the connection, which closes it. >> >> However, it is almost never the case that the GC does this before the >> pool is out of connections. So in essense you are guaranteed to get the >> connection pool is out of connections error. >> >> "J L" <j***@marymonte.com> wrote in message >> news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>> One more question....if the DataReader goes out of scope before it is >>> closed....what happens? >>> >>> John >>> >>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>> wrote: >>> >>>>Missing the fact that you are relying on the consumer of the function to >>>>remember to close the reader when they are done. >>>> >>>>Someone forgets to close it in one place, and before you know it you are >>>>tracking down a connection pool out of connections leak in your program. >>>>You >>>>would be surprised how often that happens. >>>> >>>>"J L" <j***@marymonte.com> wrote in message >>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>> Hi Marina, >>>>> Why do you say not to return a DataReader. If she uses the >>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>> What am I missing? >>>>> >>>>> TIA >>>>> John >>>>> >>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>> wrote: >>>>> >>>>>>If you are returning the reader, you have to wait for the user to >>>>>>close >>>>>>the >>>>>>reader. In order for closing the reader to close the connection, you >>>>>>have >>>>>>to >>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>> >>>>>>However, this still means the user of this function has to remember to >>>>>>close >>>>>>it. >>>>>> >>>>>>None of the code after the Return statement in your function will >>>>>>execute, >>>>>>the 'Return' statement immediately exits the function. >>>>>> >>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>> >>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>> Hi all >>>>>>> I want to return OleDbDataReader from a static function, >>>>>>> So I will have DB interface for my Entire project, >>>>>>> Is it possible? >>>>>>> How do I close the connection ?????? >>>>>>> >>>>>>> Thank you >>>>>>> Sharon >>>>>>> >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> //Example of use : >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>> ContactName, >>>>>>> FROM Customers") >>>>>>> While (reader.Read()){ >>>>>>> >>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + >>>>>>> " : >>>>>>> " >>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>> } >>>>>>> >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> //select function : >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>> { >>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>> "Data Source=C:\\Program >>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>> >>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>> >>>>>>> 'Open the connection. >>>>>>> cn.Open() >>>>>>> >>>>>>> 'Use a variable to hold the SQL statement. >>>>>>> String As String = >>>>>>> >>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>> >>>>>>> Return cmd.ExecuteReader() >>>>>>> >>>>>>> 'Close the reader and the related connection. >>>>>>> // reader.Close() >>>>>>> //?????????????????????????????????????????????????? >>>>>>> cn.Close() >>>>>>> >>>>>>> } >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >> > > Hi marina
Well in Sushil's replay she says : "DataTable is a disconnected data cache. In your case, if the data is small, it makes sense to cache it and then pass it to the user. " so what i'm asking is DataSet is the same thing ? can i write : Public static DataSet Select (string selectString) { "Data Source=C:\\Program Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" OleDbConnection cn = New OleDbConnection(connectString) cn.Open() dAdapter = new OleDbDataAdapter(sqlStr,myConn); DataSet dset = new DataSet(); dAdapter.Fill(dset); cn.Close() return dset; } And run hundred’s of calls to this function even on Access db, without worrying?? Thank you Sharon Show quote "Marina" <someone@nospam.com> wrote in message news:%23Udr78WNFHA.3296@TK2MSFTNGP15.phx.gbl... > Nothing is getting cached. I am not sure what you mean. Caching was not at > all discussed in this thread. > > "Sharon" <Sharon***@hotmail.com> wrote in message > news:eScAT9VNFHA.1172@TK2MSFTNGP12.phx.gbl... >> How about Dataset ? >> >> Is this a cashed too? >> >> >> >> "Marina" <someone@nospam.com> wrote in message >> news:%23s8r7nTNFHA.940@TK2MSFTNGP09.phx.gbl... >>> The connection stays open until the GC decides to collect it. In which >>> case, the Dispose would get called on the connection, which closes it. >>> >>> However, it is almost never the case that the GC does this before the >>> pool is out of connections. So in essense you are guaranteed to get the >>> connection pool is out of connections error. >>> >>> "J L" <j***@marymonte.com> wrote in message >>> news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>>> One more question....if the DataReader goes out of scope before it is >>>> closed....what happens? >>>> >>>> John >>>> >>>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>>> wrote: >>>> >>>>>Missing the fact that you are relying on the consumer of the function >>>>>to >>>>>remember to close the reader when they are done. >>>>> >>>>>Someone forgets to close it in one place, and before you know it you >>>>>are >>>>>tracking down a connection pool out of connections leak in your >>>>>program. You >>>>>would be surprised how often that happens. >>>>> >>>>>"J L" <j***@marymonte.com> wrote in message >>>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>>> Hi Marina, >>>>>> Why do you say not to return a DataReader. If she uses the >>>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>>> What am I missing? >>>>>> >>>>>> TIA >>>>>> John >>>>>> >>>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>>> wrote: >>>>>> >>>>>>>If you are returning the reader, you have to wait for the user to >>>>>>>close >>>>>>>the >>>>>>>reader. In order for closing the reader to close the connection, you >>>>>>>have >>>>>>>to >>>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>>> >>>>>>>However, this still means the user of this function has to remember >>>>>>>to >>>>>>>close >>>>>>>it. >>>>>>> >>>>>>>None of the code after the Return statement in your function will >>>>>>>execute, >>>>>>>the 'Return' statement immediately exits the function. >>>>>>> >>>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>>> >>>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>>> Hi all >>>>>>>> I want to return OleDbDataReader from a static function, >>>>>>>> So I will have DB interface for my Entire project, >>>>>>>> Is it possible? >>>>>>>> How do I close the connection ?????? >>>>>>>> >>>>>>>> Thank you >>>>>>>> Sharon >>>>>>>> >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> //Example of use : >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>>> ContactName, >>>>>>>> FROM Customers") >>>>>>>> While (reader.Read()){ >>>>>>>> >>>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() >>>>>>>> + " : >>>>>>>> " >>>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>>> } >>>>>>>> >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> //select function : >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>>> { >>>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>>> "Data Source=C:\\Program >>>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>>> >>>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>>> >>>>>>>> 'Open the connection. >>>>>>>> cn.Open() >>>>>>>> >>>>>>>> 'Use a variable to hold the SQL statement. >>>>>>>> String As String = >>>>>>>> >>>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>>> >>>>>>>> Return cmd.ExecuteReader() >>>>>>>> >>>>>>>> 'Close the reader and the related connection. >>>>>>>> // reader.Close() >>>>>>>> //?????????????????????????????????????????????????? >>>>>>>> cn.Close() >>>>>>>> >>>>>>>> } >>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >>> >> >> > > Cache was used to mean a local copy of the data in memory.
If you call that function 100 times, you will 100 copies of the datasets in memory. The .NET runtime would have no way of knowing the same exact dataset exists elsewhere, that it was created by running the same query on the same database. Not to mention, it would not know that you indeed want to reuse the one instance. Show quote "Sharon" <Sharon***@hotmail.com> wrote in message news:%23Qy1fhhNFHA.3380@TK2MSFTNGP15.phx.gbl... > Hi marina > > Well in Sushil's replay she says : > > > > "DataTable is a disconnected data cache. In your case, if the data is > small, it makes sense to cache it and then pass it to the user. " > > > > > > so what i'm asking is DataSet is the same thing ? > > can i write : > > Public static DataSet Select (string selectString) > { > > "Data Source=C:\\Program Files\\Microsoft Visual > Studio\\VB98\\NWIND.MDB" > OleDbConnection cn = New OleDbConnection(connectString) > cn.Open() > dAdapter = new OleDbDataAdapter(sqlStr,myConn); > DataSet dset = new DataSet(); > dAdapter.Fill(dset); > cn.Close() > > > > return dset; > > } > > > > And run hundred's of calls to this function even on Access db, without > worrying?? > > Thank you > > Sharon > > > > > > > "Marina" <someone@nospam.com> wrote in message > news:%23Udr78WNFHA.3296@TK2MSFTNGP15.phx.gbl... >> Nothing is getting cached. I am not sure what you mean. Caching was not >> at all discussed in this thread. >> >> "Sharon" <Sharon***@hotmail.com> wrote in message >> news:eScAT9VNFHA.1172@TK2MSFTNGP12.phx.gbl... >>> How about Dataset ? >>> >>> Is this a cashed too? >>> >>> >>> >>> "Marina" <someone@nospam.com> wrote in message >>> news:%23s8r7nTNFHA.940@TK2MSFTNGP09.phx.gbl... >>>> The connection stays open until the GC decides to collect it. In which >>>> case, the Dispose would get called on the connection, which closes it. >>>> >>>> However, it is almost never the case that the GC does this before the >>>> pool is out of connections. So in essense you are guaranteed to get the >>>> connection pool is out of connections error. >>>> >>>> "J L" <j***@marymonte.com> wrote in message >>>> news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>>>> One more question....if the DataReader goes out of scope before it is >>>>> closed....what happens? >>>>> >>>>> John >>>>> >>>>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>>>> wrote: >>>>> >>>>>>Missing the fact that you are relying on the consumer of the function >>>>>>to >>>>>>remember to close the reader when they are done. >>>>>> >>>>>>Someone forgets to close it in one place, and before you know it you >>>>>>are >>>>>>tracking down a connection pool out of connections leak in your >>>>>>program. You >>>>>>would be surprised how often that happens. >>>>>> >>>>>>"J L" <j***@marymonte.com> wrote in message >>>>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>>>> Hi Marina, >>>>>>> Why do you say not to return a DataReader. If she uses the >>>>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>>>> What am I missing? >>>>>>> >>>>>>> TIA >>>>>>> John >>>>>>> >>>>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>>>> wrote: >>>>>>> >>>>>>>>If you are returning the reader, you have to wait for the user to >>>>>>>>close >>>>>>>>the >>>>>>>>reader. In order for closing the reader to close the connection, you >>>>>>>>have >>>>>>>>to >>>>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>>>> >>>>>>>>However, this still means the user of this function has to remember >>>>>>>>to >>>>>>>>close >>>>>>>>it. >>>>>>>> >>>>>>>>None of the code after the Return statement in your function will >>>>>>>>execute, >>>>>>>>the 'Return' statement immediately exits the function. >>>>>>>> >>>>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>>>> >>>>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>>>> Hi all >>>>>>>>> I want to return OleDbDataReader from a static function, >>>>>>>>> So I will have DB interface for my Entire project, >>>>>>>>> Is it possible? >>>>>>>>> How do I close the connection ?????? >>>>>>>>> >>>>>>>>> Thank you >>>>>>>>> Sharon >>>>>>>>> >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> //Example of use : >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>>>> ContactName, >>>>>>>>> FROM Customers") >>>>>>>>> While (reader.Read()){ >>>>>>>>> >>>>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() >>>>>>>>> + " : >>>>>>>>> " >>>>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>>>> } >>>>>>>>> >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> //select function : >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>>>> { >>>>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>>>> "Data Source=C:\\Program >>>>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>>>> >>>>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>>>> >>>>>>>>> 'Open the connection. >>>>>>>>> cn.Open() >>>>>>>>> >>>>>>>>> 'Use a variable to hold the SQL statement. >>>>>>>>> String As String = >>>>>>>>> >>>>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>>>> >>>>>>>>> Return cmd.ExecuteReader() >>>>>>>>> >>>>>>>>> 'Close the reader and the related connection. >>>>>>>>> // reader.Close() >>>>>>>>> //?????????????????????????????????????????????????? >>>>>>>>> cn.Close() >>>>>>>>> >>>>>>>>> } >>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>>> >>> >>> >> >> > > You do not need to worry about disposing DataSet unless you explicitly
create command/connection objects when u create the DataSet, which u shouldnt need to do in most cases. HTH, Premier JiangZemin Show quote "Sharon" <Sharon***@hotmail.com> wrote in message news:eScAT9VNFHA.1172@TK2MSFTNGP12.phx.gbl... > How about Dataset ? > > Is this a cashed too? > > > > "Marina" <someone@nospam.com> wrote in message > news:%23s8r7nTNFHA.940@TK2MSFTNGP09.phx.gbl... >> The connection stays open until the GC decides to collect it. In which >> case, the Dispose would get called on the connection, which closes it. >> >> However, it is almost never the case that the GC does this before the >> pool is out of connections. So in essense you are guaranteed to get the >> connection pool is out of connections error. >> >> "J L" <j***@marymonte.com> wrote in message >> news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>> One more question....if the DataReader goes out of scope before it is >>> closed....what happens? >>> >>> John >>> >>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>> wrote: >>> >>>>Missing the fact that you are relying on the consumer of the function to >>>>remember to close the reader when they are done. >>>> >>>>Someone forgets to close it in one place, and before you know it you are >>>>tracking down a connection pool out of connections leak in your program. >>>>You >>>>would be surprised how often that happens. >>>> >>>>"J L" <j***@marymonte.com> wrote in message >>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>> Hi Marina, >>>>> Why do you say not to return a DataReader. If she uses the >>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>> What am I missing? >>>>> >>>>> TIA >>>>> John >>>>> >>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>> wrote: >>>>> >>>>>>If you are returning the reader, you have to wait for the user to >>>>>>close >>>>>>the >>>>>>reader. In order for closing the reader to close the connection, you >>>>>>have >>>>>>to >>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>> >>>>>>However, this still means the user of this function has to remember to >>>>>>close >>>>>>it. >>>>>> >>>>>>None of the code after the Return statement in your function will >>>>>>execute, >>>>>>the 'Return' statement immediately exits the function. >>>>>> >>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>> >>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>> Hi all >>>>>>> I want to return OleDbDataReader from a static function, >>>>>>> So I will have DB interface for my Entire project, >>>>>>> Is it possible? >>>>>>> How do I close the connection ?????? >>>>>>> >>>>>>> Thank you >>>>>>> Sharon >>>>>>> >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> //Example of use : >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>> ContactName, >>>>>>> FROM Customers") >>>>>>> While (reader.Read()){ >>>>>>> >>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + >>>>>>> " : >>>>>>> " >>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>> } >>>>>>> >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> //select function : >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>> { >>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>> "Data Source=C:\\Program >>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>> >>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>> >>>>>>> 'Open the connection. >>>>>>> cn.Open() >>>>>>> >>>>>>> 'Use a variable to hold the SQL statement. >>>>>>> String As String = >>>>>>> >>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>> >>>>>>> Return cmd.ExecuteReader() >>>>>>> >>>>>>> 'Close the reader and the related connection. >>>>>>> // reader.Close() >>>>>>> //?????????????????????????????????????????????????? >>>>>>> cn.Close() >>>>>>> >>>>>>> } >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >> > > Hi Marina,
I hope I am not trying your patience but I have one more question... I have a DAL that I implemented as follows (psecudo code) try if dbProvider = "OleDb" then dim cn as new OleDbConnection(myconnectstring) <I then use this connection to fill a dataset> elseif dbProvider = "SqlDb" then dim cn as new SqlConnection(myconnectstring) <I then use this connection to fill a dataset> end if catch ex as Exception Throw New SystemException("some info here", ex) <for example a bad SQL statement provide to my command object> end try My question is what happens if there is an exception. I can not reference the connection in the catch block to see if it is open and close it. So what happens to the connection in this case? And how best to handle this situation? TIA, John Show quote On Wed, 30 Mar 2005 10:05:57 -0500, "Marina" <someone@nospam.com> wrote: >The connection stays open until the GC decides to collect it. In which case, >the Dispose would get called on the connection, which closes it. > >However, it is almost never the case that the GC does this before the pool >is out of connections. So in essense you are guaranteed to get the >connection pool is out of connections error. > >"J L" <j***@marymonte.com> wrote in message >news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >> One more question....if the DataReader goes out of scope before it is >> closed....what happens? >> >> John >> >> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >> wrote: >> >>>Missing the fact that you are relying on the consumer of the function to >>>remember to close the reader when they are done. >>> >>>Someone forgets to close it in one place, and before you know it you are >>>tracking down a connection pool out of connections leak in your program. >>>You >>>would be surprised how often that happens. >>> >>>"J L" <j***@marymonte.com> wrote in message >>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>> Hi Marina, >>>> Why do you say not to return a DataReader. If she uses the >>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>> What am I missing? >>>> >>>> TIA >>>> John >>>> >>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>> wrote: >>>> >>>>>If you are returning the reader, you have to wait for the user to close >>>>>the >>>>>reader. In order for closing the reader to close the connection, you >>>>>have >>>>>to >>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>> >>>>>However, this still means the user of this function has to remember to >>>>>close >>>>>it. >>>>> >>>>>None of the code after the Return statement in your function will >>>>>execute, >>>>>the 'Return' statement immediately exits the function. >>>>> >>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>> >>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>> Hi all >>>>>> I want to return OleDbDataReader from a static function, >>>>>> So I will have DB interface for my Entire project, >>>>>> Is it possible? >>>>>> How do I close the connection ?????? >>>>>> >>>>>> Thank you >>>>>> Sharon >>>>>> >>>>>> ///////////////////////////////////////////////////////////// >>>>>> //Example of use : >>>>>> ///////////////////////////////////////////////////////////// >>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>> ContactName, >>>>>> FROM Customers") >>>>>> While (reader.Read()){ >>>>>> >>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + " >>>>>> : >>>>>> " >>>>>> + reader("ContactName").ToString() + "<br>") >>>>>> } >>>>>> >>>>>> ///////////////////////////////////////////////////////////// >>>>>> //select function : >>>>>> ///////////////////////////////////////////////////////////// >>>>>> Public static OleDbDataReader Select (string selectString) >>>>>> { >>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>> "Data Source=C:\\Program >>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>> >>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>> >>>>>> 'Open the connection. >>>>>> cn.Open() >>>>>> >>>>>> 'Use a variable to hold the SQL statement. >>>>>> String As String = >>>>>> >>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>> >>>>>> Return cmd.ExecuteReader() >>>>>> >>>>>> 'Close the reader and the related connection. >>>>>> // reader.Close() >>>>>> //?????????????????????????????????????????????????? >>>>>> cn.Close() >>>>>> >>>>>> } >>>>>> >>>>>> >>>>> >>>> >>> >> > You need to declare the variables outside the try block. This is just a
scoping issue. Show quote "J L" <j***@marymonte.com> wrote in message news:9idm41tubdt21jvh85rv7d4cd1r15gkh57@4ax.com... > Hi Marina, > I hope I am not trying your patience but I have one more question... > > I have a DAL that I implemented as follows (psecudo code) > > try > if dbProvider = "OleDb" then > dim cn as new OleDbConnection(myconnectstring) > <I then use this connection to fill a dataset> > > elseif dbProvider = "SqlDb" then > dim cn as new SqlConnection(myconnectstring) > <I then use this connection to fill a dataset> > > end if > catch ex as Exception > Throw New SystemException("some info here", ex) > <for example a bad SQL statement provide to my command object> > end try > > My question is what happens if there is an exception. I can not > reference the connection in the catch block to see if it is open and > close it. So what happens to the connection in this case? And how best > to handle this situation? > > TIA, > John > > On Wed, 30 Mar 2005 10:05:57 -0500, "Marina" <someone@nospam.com> > wrote: > >>The connection stays open until the GC decides to collect it. In which >>case, >>the Dispose would get called on the connection, which closes it. >> >>However, it is almost never the case that the GC does this before the pool >>is out of connections. So in essense you are guaranteed to get the >>connection pool is out of connections error. >> >>"J L" <j***@marymonte.com> wrote in message >>news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>> One more question....if the DataReader goes out of scope before it is >>> closed....what happens? >>> >>> John >>> >>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>> wrote: >>> >>>>Missing the fact that you are relying on the consumer of the function to >>>>remember to close the reader when they are done. >>>> >>>>Someone forgets to close it in one place, and before you know it you are >>>>tracking down a connection pool out of connections leak in your program. >>>>You >>>>would be surprised how often that happens. >>>> >>>>"J L" <j***@marymonte.com> wrote in message >>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>> Hi Marina, >>>>> Why do you say not to return a DataReader. If she uses the >>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>> What am I missing? >>>>> >>>>> TIA >>>>> John >>>>> >>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>> wrote: >>>>> >>>>>>If you are returning the reader, you have to wait for the user to >>>>>>close >>>>>>the >>>>>>reader. In order for closing the reader to close the connection, you >>>>>>have >>>>>>to >>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>> >>>>>>However, this still means the user of this function has to remember to >>>>>>close >>>>>>it. >>>>>> >>>>>>None of the code after the Return statement in your function will >>>>>>execute, >>>>>>the 'Return' statement immediately exits the function. >>>>>> >>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>> >>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>> Hi all >>>>>>> I want to return OleDbDataReader from a static function, >>>>>>> So I will have DB interface for my Entire project, >>>>>>> Is it possible? >>>>>>> How do I close the connection ?????? >>>>>>> >>>>>>> Thank you >>>>>>> Sharon >>>>>>> >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> //Example of use : >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>> ContactName, >>>>>>> FROM Customers") >>>>>>> While (reader.Read()){ >>>>>>> >>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + >>>>>>> " >>>>>>> : >>>>>>> " >>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>> } >>>>>>> >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> //select function : >>>>>>> ///////////////////////////////////////////////////////////// >>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>> { >>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>> "Data Source=C:\\Program >>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>> >>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>> >>>>>>> 'Open the connection. >>>>>>> cn.Open() >>>>>>> >>>>>>> 'Use a variable to hold the SQL statement. >>>>>>> String As String = >>>>>>> >>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>> >>>>>>> Return cmd.ExecuteReader() >>>>>>> >>>>>>> 'Close the reader and the related connection. >>>>>>> // reader.Close() >>>>>>> //?????????????????????????????????????????????????? >>>>>>> cn.Close() >>>>>>> >>>>>>> } >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> > I know it is a scoping issue but I am doing it for provider
independence. So what I guess I need to do is this dim cnOleDb as new OleDbConnection dim cnSQL as new SqlConnection Try if dbProvider = "OleDb" then <use cnOleDb in my command object> elseif dbProvider ="SqlDb" then <use cnSQL in my command object> else <throw an error for invalid provider type> endif Catch <handle the errors> Finally if cnOleDb.State = ConnectionState.Open then cnOledDb.close() end if if cnSql.State = ConnectionState.Open then cnSql.close() end if End Try Is that a good way to go? I did read about using interfaces and casting etc. but seemed very complicated. Are there any reasons not to do it this way? ("it" means provider independent) Thanks again, John Show quote On Thu, 31 Mar 2005 10:24:40 -0500, "Marina" <someone@nospam.com> wrote: >You need to declare the variables outside the try block. This is just a >scoping issue. > >"J L" <j***@marymonte.com> wrote in message >news:9idm41tubdt21jvh85rv7d4cd1r15gkh57@4ax.com... >> Hi Marina, >> I hope I am not trying your patience but I have one more question... >> >> I have a DAL that I implemented as follows (psecudo code) >> >> try >> if dbProvider = "OleDb" then >> dim cn as new OleDbConnection(myconnectstring) >> <I then use this connection to fill a dataset> >> >> elseif dbProvider = "SqlDb" then >> dim cn as new SqlConnection(myconnectstring) >> <I then use this connection to fill a dataset> >> >> end if >> catch ex as Exception >> Throw New SystemException("some info here", ex) >> <for example a bad SQL statement provide to my command object> >> end try >> >> My question is what happens if there is an exception. I can not >> reference the connection in the catch block to see if it is open and >> close it. So what happens to the connection in this case? And how best >> to handle this situation? >> >> TIA, >> John >> >> On Wed, 30 Mar 2005 10:05:57 -0500, "Marina" <someone@nospam.com> >> wrote: >> >>>The connection stays open until the GC decides to collect it. In which >>>case, >>>the Dispose would get called on the connection, which closes it. >>> >>>However, it is almost never the case that the GC does this before the pool >>>is out of connections. So in essense you are guaranteed to get the >>>connection pool is out of connections error. >>> >>>"J L" <j***@marymonte.com> wrote in message >>>news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>>> One more question....if the DataReader goes out of scope before it is >>>> closed....what happens? >>>> >>>> John >>>> >>>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>>> wrote: >>>> >>>>>Missing the fact that you are relying on the consumer of the function to >>>>>remember to close the reader when they are done. >>>>> >>>>>Someone forgets to close it in one place, and before you know it you are >>>>>tracking down a connection pool out of connections leak in your program. >>>>>You >>>>>would be surprised how often that happens. >>>>> >>>>>"J L" <j***@marymonte.com> wrote in message >>>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>>> Hi Marina, >>>>>> Why do you say not to return a DataReader. If she uses the >>>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>>> What am I missing? >>>>>> >>>>>> TIA >>>>>> John >>>>>> >>>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>>> wrote: >>>>>> >>>>>>>If you are returning the reader, you have to wait for the user to >>>>>>>close >>>>>>>the >>>>>>>reader. In order for closing the reader to close the connection, you >>>>>>>have >>>>>>>to >>>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>>> >>>>>>>However, this still means the user of this function has to remember to >>>>>>>close >>>>>>>it. >>>>>>> >>>>>>>None of the code after the Return statement in your function will >>>>>>>execute, >>>>>>>the 'Return' statement immediately exits the function. >>>>>>> >>>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>>> >>>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>>> Hi all >>>>>>>> I want to return OleDbDataReader from a static function, >>>>>>>> So I will have DB interface for my Entire project, >>>>>>>> Is it possible? >>>>>>>> How do I close the connection ?????? >>>>>>>> >>>>>>>> Thank you >>>>>>>> Sharon >>>>>>>> >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> //Example of use : >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>>> ContactName, >>>>>>>> FROM Customers") >>>>>>>> While (reader.Read()){ >>>>>>>> >>>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() + >>>>>>>> " >>>>>>>> : >>>>>>>> " >>>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>>> } >>>>>>>> >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> //select function : >>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>>> { >>>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>>> "Data Source=C:\\Program >>>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>>> >>>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>>> >>>>>>>> 'Open the connection. >>>>>>>> cn.Open() >>>>>>>> >>>>>>>> 'Use a variable to hold the SQL statement. >>>>>>>> String As String = >>>>>>>> >>>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>>> >>>>>>>> Return cmd.ExecuteReader() >>>>>>>> >>>>>>>> 'Close the reader and the related connection. >>>>>>>> // reader.Close() >>>>>>>> //?????????????????????????????????????????????????? >>>>>>>> cn.Close() >>>>>>>> >>>>>>>> } >>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> > If you were to use some provider specific API's, like the one for oracle,
etc, you could potentially end up with a large number of these. Which is why they all implement the same interfaces, so you could talk to the object without caring which specific provider it was. It's really not hard to just cast the object. And it means you don't need If statements everywhere, and you need just one variable for the connection, etc. It should simplify your code if anything. Show quote "J L" <j***@marymonte.com> wrote in message news:3s7o41dioeaoad9r2oieb79odb5cu5rjl2@4ax.com... >I know it is a scoping issue but I am doing it for provider > independence. So what I guess I need to do is this > > dim cnOleDb as new OleDbConnection > dim cnSQL as new SqlConnection > > Try > if dbProvider = "OleDb" then > <use cnOleDb in my command object> > elseif dbProvider ="SqlDb" then > <use cnSQL in my command object> > else > <throw an error for invalid provider type> > endif > Catch > <handle the errors> > Finally > if cnOleDb.State = ConnectionState.Open then > cnOledDb.close() > end if > if cnSql.State = ConnectionState.Open then > cnSql.close() > end if > End Try > > Is that a good way to go? I did read about using interfaces and > casting etc. but seemed very complicated. Are there any reasons not to > do it this way? ("it" means provider independent) > > Thanks again, > John > > > On Thu, 31 Mar 2005 10:24:40 -0500, "Marina" <someone@nospam.com> > wrote: > >>You need to declare the variables outside the try block. This is just a >>scoping issue. >> >>"J L" <j***@marymonte.com> wrote in message >>news:9idm41tubdt21jvh85rv7d4cd1r15gkh57@4ax.com... >>> Hi Marina, >>> I hope I am not trying your patience but I have one more question... >>> >>> I have a DAL that I implemented as follows (psecudo code) >>> >>> try >>> if dbProvider = "OleDb" then >>> dim cn as new OleDbConnection(myconnectstring) >>> <I then use this connection to fill a dataset> >>> >>> elseif dbProvider = "SqlDb" then >>> dim cn as new SqlConnection(myconnectstring) >>> <I then use this connection to fill a dataset> >>> >>> end if >>> catch ex as Exception >>> Throw New SystemException("some info here", ex) >>> <for example a bad SQL statement provide to my command object> >>> end try >>> >>> My question is what happens if there is an exception. I can not >>> reference the connection in the catch block to see if it is open and >>> close it. So what happens to the connection in this case? And how best >>> to handle this situation? >>> >>> TIA, >>> John >>> >>> On Wed, 30 Mar 2005 10:05:57 -0500, "Marina" <someone@nospam.com> >>> wrote: >>> >>>>The connection stays open until the GC decides to collect it. In which >>>>case, >>>>the Dispose would get called on the connection, which closes it. >>>> >>>>However, it is almost never the case that the GC does this before the >>>>pool >>>>is out of connections. So in essense you are guaranteed to get the >>>>connection pool is out of connections error. >>>> >>>>"J L" <j***@marymonte.com> wrote in message >>>>news:i1fl41h7d5c062qu46j30jgjeh7ttptcmj@4ax.com... >>>>> One more question....if the DataReader goes out of scope before it is >>>>> closed....what happens? >>>>> >>>>> John >>>>> >>>>> On Wed, 30 Mar 2005 09:12:17 -0500, "Marina" <someone@nospam.com> >>>>> wrote: >>>>> >>>>>>Missing the fact that you are relying on the consumer of the function >>>>>>to >>>>>>remember to close the reader when they are done. >>>>>> >>>>>>Someone forgets to close it in one place, and before you know it you >>>>>>are >>>>>>tracking down a connection pool out of connections leak in your >>>>>>program. >>>>>>You >>>>>>would be surprised how often that happens. >>>>>> >>>>>>"J L" <j***@marymonte.com> wrote in message >>>>>>news:eqdk41d9q0ce35itf2lq30errrtniom51g@4ax.com... >>>>>>> Hi Marina, >>>>>>> Why do you say not to return a DataReader. If she uses the >>>>>>> CommandBehavior.CloseConnection, I can see no reason not to use it. >>>>>>> What am I missing? >>>>>>> >>>>>>> TIA >>>>>>> John >>>>>>> >>>>>>> On Tue, 29 Mar 2005 16:13:42 -0500, "Marina" <someone@nospam.com> >>>>>>> wrote: >>>>>>> >>>>>>>>If you are returning the reader, you have to wait for the user to >>>>>>>>close >>>>>>>>the >>>>>>>>reader. In order for closing the reader to close the connection, you >>>>>>>>have >>>>>>>>to >>>>>>>>pass in CommandBehavior.CloseConnection into ExecuteReader. >>>>>>>> >>>>>>>>However, this still means the user of this function has to remember >>>>>>>>to >>>>>>>>close >>>>>>>>it. >>>>>>>> >>>>>>>>None of the code after the Return statement in your function will >>>>>>>>execute, >>>>>>>>the 'Return' statement immediately exits the function. >>>>>>>> >>>>>>>>In general, the rule of thumb is don't do this. Return datatables. >>>>>>>> >>>>>>>>"Sharon" <Sharon***@hotmail.com> wrote in message >>>>>>>>news:%233EWa3JNFHA.1176@TK2MSFTNGP15.phx.gbl... >>>>>>>>> Hi all >>>>>>>>> I want to return OleDbDataReader from a static function, >>>>>>>>> So I will have DB interface for my Entire project, >>>>>>>>> Is it possible? >>>>>>>>> How do I close the connection ?????? >>>>>>>>> >>>>>>>>> Thank you >>>>>>>>> Sharon >>>>>>>>> >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> //Example of use : >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> OleDbDataReader reader = myDbObj.Select("SELECT CustomerID, >>>>>>>>> ContactName, >>>>>>>>> FROM Customers") >>>>>>>>> While (reader.Read()){ >>>>>>>>> >>>>>>>>> System.diagnostics.Trace.WriteLine(reader("CustomerID").ToString() >>>>>>>>> + >>>>>>>>> " >>>>>>>>> : >>>>>>>>> " >>>>>>>>> + reader("ContactName").ToString() + "<br>") >>>>>>>>> } >>>>>>>>> >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> //select function : >>>>>>>>> ///////////////////////////////////////////////////////////// >>>>>>>>> Public static OleDbDataReader Select (string selectString) >>>>>>>>> { >>>>>>>>> 'Use a string variable to hold the ConnectionString property. >>>>>>>>> String connectString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _ >>>>>>>>> "Data Source=C:\\Program >>>>>>>>> Files\\Microsoft Visual Studio\\VB98\\NWIND.MDB" >>>>>>>>> >>>>>>>>> OleDbConnection cn = New OleDbConnection(connectString) >>>>>>>>> >>>>>>>>> 'Open the connection. >>>>>>>>> cn.Open() >>>>>>>>> >>>>>>>>> 'Use a variable to hold the SQL statement. >>>>>>>>> String As String = >>>>>>>>> >>>>>>>>> OleDbCommand cmd = New OleDbCommand(selectString, cn) >>>>>>>>> >>>>>>>>> Return cmd.ExecuteReader() >>>>>>>>> >>>>>>>>> 'Close the reader and the related connection. >>>>>>>>> // reader.Close() >>>>>>>>> //?????????????????????????????????????????????????? >>>>>>>>> cn.Close() >>>>>>>>> >>>>>>>>> } >>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >  |
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