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DataColumn ExpressionsI have a typed DataSet with a DataTable where I added a column FullName that
simply returns the concatination of 2 other columns FirstName and LastName. There is also a DataAdapter that returns this DataTable populated from the DataBase. If i Preview this data from the DataSet Designer, everything shows up fine and that's the only case where the FullName expression shows up. If I call the Adapter methods to populate the DataTable, the expression FullName column is NULL. Please help. All I want to do is have an extra column in a datatable with an expression set in design time. This works if I add the column programatically after the datatable is filled up. If it is not a bound column, you can format it in the CellFormatting event.
Like this: Put this in your form_load: AddHandler m_Grid.CellFormatting, AddressOf OnCellFormatting Private Sub OnCellFormatting(ByVal sender As Object, _ ByVal e As DataGridViewCellFormattingEventArgs) 'The event arg that is passed in exposes a number of ' properties to let you know what cell is being rendered. 'You can use the ColumnIndex to determine which column ' the event is being fired for. 'Note: if you were really going to do something like this, ' you would look up the column once and save the col#, ' and then use that value in this routine. Accessing it ' using the name repeatedly will slow it down. If e.ColumnIndex = m_Grid.Columns("FullName").Index 'Setting this to true signals the grid that this ' column is being dynamically updated. If you don't ' do this, you will get an infinite loop if you have ' also set the column to have its size automatically determined. e.FormattingApplied = True 'Get the row being populated. Format this cell. Dim row As DataGridViewRow = m_Grid.Rows(e.RowIndex) e.Value = String.Format("{0} {1}", _ row.Cells("FirstName").Value, _ row.Cells("LastName").Value) End If End Sub Robin S. ---------------------------------- Show quote "Lorenc" <Lor***@discussions.microsoft.com> wrote in message news:6172F783-01A7-4E72-805D-CCCF7892D679@microsoft.com... >I have a typed DataSet with a DataTable where I added a column FullName >that > simply returns the concatination of 2 other columns FirstName and > LastName. > There is also a DataAdapter that returns this DataTable populated from the > DataBase. > If i Preview this data from the DataSet Designer, everything shows up fine > and that's the only case where the FullName expression shows up. If I call > the Adapter methods to populate the DataTable, the expression FullName > column > is NULL. > Please help. All I want to do is have an extra column in a datatable with > an > expression set in design time. This works if I add the column > programatically > after the datatable is filled up. > Lorenc,
I don't think that one of us can real help you with a piece of code. Be aware as well that there are two methods that you are doing. One concatentation is done in the SQL transaction code the other one is done in the selection. You write in the subject Expression. So probably it is that, can you show that? Cor Show quote "Lorenc" <Lor***@discussions.microsoft.com> schreef in bericht news:6172F783-01A7-4E72-805D-CCCF7892D679@microsoft.com... >I have a typed DataSet with a DataTable where I added a column FullName >that > simply returns the concatination of 2 other columns FirstName and > LastName. > There is also a DataAdapter that returns this DataTable populated from the > DataBase. > If i Preview this data from the DataSet Designer, everything shows up fine > and that's the only case where the FullName expression shows up. If I call > the Adapter methods to populate the DataTable, the expression FullName > column > is NULL. > Please help. All I want to do is have an extra column in a datatable with > an > expression set in design time. This works if I add the column > programatically > after the datatable is filled up. > Thank you RobinS and Cor for your responses.
My problem is a very simple case. I know I can format the column for the fullname and I know I can do that in many ways through SQL, but it is very handy if you have this computed column in the datatable and keep sql and codebehind clean. To replicate the problem, just create a simple typed DataSet and add a datatable based on a database table, which has let's say 2 columns, first and last name. As you know, you also get a table adapter that populates this datatable. Now, add a column to the datatable(in the dataset design) called fullname and set the expression on that column to FirstName + ' ' + LastName in the property of the fullname column (I am using Visual Studio 2005). Right click on the adapter (usually below the datatable) and select preview, you will now see that fullname is calculated fine. Now, create a webform and add a gridview with a datasource from this datatable. You will now see that the fullname is empty (DBNull to be precise). Is this a bug? I am frustrated with this one because this is how Microsoft suggests creating computed columns and it is a very simple logic thing to do. Notice that if you add a new column programmatically to the datatable and not from the design it works fine. Why the difference? Maybe I am doing something wrong, but this is one of those cases that you spend days searching forums and the web for a solution to make something work for a framework that it's life span is maybe 2-3 years. What is funny and sad in the same time is that I have just establish a nice way of creating a data access layer and a business logic layer that works for my applications in .NET 1.1 based on best practices which are now obsolete with .NET 2. Again, based on best practices I am trying to establish a nice data access layer using typed datasets because they are so nice in .NET2 and I bet that in .NET 3 that is coming up next year with that windows workflow what I am doing now will be obsolete as well. This is what I call a worthy experience. Show quote "Cor Ligthert [MVP]" wrote: > Lorenc, > > I don't think that one of us can real help you with a piece of code. Be > aware as well that there are two methods that you are doing. One > concatentation is done in the SQL transaction code the other one is done in > the selection. You write in the subject Expression. So probably it is that, > can you show that? > > Cor > > "Lorenc" <Lor***@discussions.microsoft.com> schreef in bericht > news:6172F783-01A7-4E72-805D-CCCF7892D679@microsoft.com... > >I have a typed DataSet with a DataTable where I added a column FullName > >that > > simply returns the concatination of 2 other columns FirstName and > > LastName. > > There is also a DataAdapter that returns this DataTable populated from the > > DataBase. > > If i Preview this data from the DataSet Designer, everything shows up fine > > and that's the only case where the FullName expression shows up. If I call > > the Adapter methods to populate the DataTable, the expression FullName > > column > > is NULL. > > Please help. All I want to do is have an extra column in a datatable with > > an > > expression set in design time. This works if I add the column > > programatically > > after the datatable is filled up. > > > > > Lorenc,
At least it is " " and not ' ', I have done this often, it should go. Cor Show quote "Lorenc" <Lor***@discussions.microsoft.com> schreef in bericht news:201F08B9-6403-48A6-8712-637669F12FA6@microsoft.com... > Thank you RobinS and Cor for your responses. > My problem is a very simple case. I know I can format the column for the > fullname and I know I can do that in many ways through SQL, but it is very > handy if you have this computed column in the datatable and keep sql and > codebehind clean. > To replicate the problem, just create a simple typed DataSet and add a > datatable based on a database table, which has let's say 2 columns, first > and > last name. As you know, you also get a table adapter that populates this > datatable. Now, add a column to the datatable(in the dataset design) > called > fullname and set the expression on that column to FirstName + ' ' + > LastName > in the property of the fullname column (I am using Visual Studio 2005). > Right click on the adapter (usually below the datatable) and select > preview, you will now see that fullname is calculated fine. Now, create a > webform and add a gridview with a datasource from this datatable. You will > now see that the fullname is empty (DBNull to be precise). Is this a bug? > I am frustrated with this one because this is how Microsoft suggests > creating computed columns and it is a very simple logic thing to do. > Notice > that if you add a new column programmatically to the datatable and not > from > the design it works fine. Why the difference? > Maybe I am doing something wrong, but this is one of those cases that you > spend days searching forums and the web for a solution to make something > work > for a framework that it's life span is maybe 2-3 years. > What is funny and sad in the same time is that I have just establish a > nice > way of creating a data access layer and a business logic layer that works > for > my applications in .NET 1.1 based on best practices which are now obsolete > with .NET 2. Again, based on best practices I am trying to establish a > nice > data access layer using typed datasets because they are so nice in .NET2 > and > I bet that in .NET 3 that is coming up next year with that windows > workflow > what I am doing now will be obsolete as well. This is what I call a worthy > experience. > > > "Cor Ligthert [MVP]" wrote: > >> Lorenc, >> >> I don't think that one of us can real help you with a piece of code. Be >> aware as well that there are two methods that you are doing. One >> concatentation is done in the SQL transaction code the other one is done >> in >> the selection. You write in the subject Expression. So probably it is >> that, >> can you show that? >> >> Cor >> >> "Lorenc" <Lor***@discussions.microsoft.com> schreef in bericht >> news:6172F783-01A7-4E72-805D-CCCF7892D679@microsoft.com... >> >I have a typed DataSet with a DataTable where I added a column FullName >> >that >> > simply returns the concatination of 2 other columns FirstName and >> > LastName. >> > There is also a DataAdapter that returns this DataTable populated from >> > the >> > DataBase. >> > If i Preview this data from the DataSet Designer, everything shows up >> > fine >> > and that's the only case where the FullName expression shows up. If I >> > call >> > the Adapter methods to populate the DataTable, the expression FullName >> > column >> > is NULL. >> > Please help. All I want to do is have an extra column in a datatable >> > with >> > an >> > expression set in design time. This works if I add the column >> > programatically >> > after the datatable is filled up. >> > >> >> >> Thanks Cor.
That's not it. You can't use " ", you will get a property is not valid message right away, you have to use single quotes. I did find a work around though. I added the following partial class which extends the dataset class and it is all good. Again You can't put expression value at the design time, you have to do it in code otherwise it gets lost. public partial class ContactDataSet { public partial class ContactDataTable { public override void EndInit() { base.EndInit(); FullNameColumn.Expression = "FirstName + ' ' + LastName"; } } } Show quote "Cor Ligthert [MVP]" wrote: > Lorenc, > > At least it is " " and not ' ', I have done this often, it should go. > > Cor > > "Lorenc" <Lor***@discussions.microsoft.com> schreef in bericht > news:201F08B9-6403-48A6-8712-637669F12FA6@microsoft.com... > > Thank you RobinS and Cor for your responses. > > My problem is a very simple case. I know I can format the column for the > > fullname and I know I can do that in many ways through SQL, but it is very > > handy if you have this computed column in the datatable and keep sql and > > codebehind clean. > > To replicate the problem, just create a simple typed DataSet and add a > > datatable based on a database table, which has let's say 2 columns, first > > and > > last name. As you know, you also get a table adapter that populates this > > datatable. Now, add a column to the datatable(in the dataset design) > > called > > fullname and set the expression on that column to FirstName + ' ' + > > LastName > > in the property of the fullname column (I am using Visual Studio 2005). > > Right click on the adapter (usually below the datatable) and select > > preview, you will now see that fullname is calculated fine. Now, create a > > webform and add a gridview with a datasource from this datatable. You will > > now see that the fullname is empty (DBNull to be precise). Is this a bug? > > I am frustrated with this one because this is how Microsoft suggests > > creating computed columns and it is a very simple logic thing to do. > > Notice > > that if you add a new column programmatically to the datatable and not > > from > > the design it works fine. Why the difference? > > Maybe I am doing something wrong, but this is one of those cases that you > > spend days searching forums and the web for a solution to make something > > work > > for a framework that it's life span is maybe 2-3 years. > > What is funny and sad in the same time is that I have just establish a > > nice > > way of creating a data access layer and a business logic layer that works > > for > > my applications in .NET 1.1 based on best practices which are now obsolete > > with .NET 2. Again, based on best practices I am trying to establish a > > nice > > data access layer using typed datasets because they are so nice in .NET2 > > and > > I bet that in .NET 3 that is coming up next year with that windows > > workflow > > what I am doing now will be obsolete as well. This is what I call a worthy > > experience. > > > > > > "Cor Ligthert [MVP]" wrote: > > > >> Lorenc, > >> > >> I don't think that one of us can real help you with a piece of code. Be > >> aware as well that there are two methods that you are doing. One > >> concatentation is done in the SQL transaction code the other one is done > >> in > >> the selection. You write in the subject Expression. So probably it is > >> that, > >> can you show that? > >> > >> Cor > >> > >> "Lorenc" <Lor***@discussions.microsoft.com> schreef in bericht > >> news:6172F783-01A7-4E72-805D-CCCF7892D679@microsoft.com... > >> >I have a typed DataSet with a DataTable where I added a column FullName > >> >that > >> > simply returns the concatination of 2 other columns FirstName and > >> > LastName. > >> > There is also a DataAdapter that returns this DataTable populated from > >> > the > >> > DataBase. > >> > If i Preview this data from the DataSet Designer, everything shows up > >> > fine > >> > and that's the only case where the FullName expression shows up. If I > >> > call > >> > the Adapter methods to populate the DataTable, the expression FullName > >> > column > >> > is NULL. > >> > Please help. All I want to do is have an extra column in a datatable > >> > with > >> > an > >> > expression set in design time. This works if I add the column > >> > programatically > >> > after the datatable is filled up. > >> > > >> > >> > >> > > >  |
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