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Reflection and variable selection? Late binding?I learned that for my.sttings, I can pull an entry by name, but can I use reflection to load a varaible? Example void dosomething(string variablename) // note: value passed in for variable name is "foo" int foo=1 int bar=2 messagebox.show(reflectionhere(variablename)); I want 1 to show up. Is this possible? Is this what late binding is? There are circumstances where it'd be nice to construct a string which will represent a varaible name that I'd like to use. Thank you... -Ben Hi Ben,
No reflection or binding needed: string text = null; switch (variableName) { case "foo": text = foo.ToString(); break; case "bar": text = bar.ToString(); break; } MessageBox.Show(text); I'm not sure it's such a good idea to pass in the name of a local variable though. An Enum would be appropriate here instead: enum DoSomethingChoice { Foo, Bar } class FooBarChoiceTest { int foo = 1, bar = 2; void DoSomething(DoSomethingChoice choice) { string text = null; switch (choice) { case DoSomethingChoice.Foo: text = foo.ToString(); break; case DoSomethingChoice.Bar: text = bar.ToString(); break; default: throw new System.ComponentModel.InvalidEnumArgumentException( "choice", (int) choice, typeof(DoSomethingChoice)); } MessageBox.Show(text); } } -- Show quoteDave Sexton "Ben R." <benr@newsgroup.nospam> wrote in message news:AF6EED6C-7C1C-4C7B-93D2-2A01231C7552@microsoft.com... > Hi, > > I learned that for my.sttings, I can pull an entry by name, but can I use > reflection to load a varaible? Example > > void dosomething(string variablename) > // note: value passed in for variable name is "foo" > int foo=1 > int bar=2 > > messagebox.show(reflectionhere(variablename)); > > I want 1 to show up. > > Is this possible? Is this what late binding is? There are circumstances > where it'd be nice to construct a string which will represent a varaible name > that I'd like to use. > > Thank you... > > -Ben > > > Hey Dave,
Thanks for the response. I was thinking about putting in the switching logic you suggested, but I'm wondering if this can be avoided. I'm considering a situation where I have many different variables that could be used, instead of just 2. It seems silly to have to write switching logic for each variable when each case is doing something very similar: going from string "x" to variable x. Is there any way you know of to accomplish this without explicit switching logic? -Ben Show quote "Dave Sexton" wrote: > Hi Ben, > > No reflection or binding needed: > > string text = null; > > switch (variableName) > { > case "foo": > text = foo.ToString(); > break; > case "bar": > text = bar.ToString(); > break; > } > > MessageBox.Show(text); > > > I'm not sure it's such a good idea to pass in the name of a local variable though. An Enum would be appropriate here instead: > > enum DoSomethingChoice > { > Foo, > Bar > } > > class FooBarChoiceTest > { > int foo = 1, bar = 2; > > void DoSomething(DoSomethingChoice choice) > { > string text = null; > > switch (choice) > { > case DoSomethingChoice.Foo: > text = foo.ToString(); > break; > case DoSomethingChoice.Bar: > text = bar.ToString(); > break; > default: > throw new System.ComponentModel.InvalidEnumArgumentException( > "choice", (int) choice, typeof(DoSomethingChoice)); > } > > MessageBox.Show(text); > } > } > > -- > Dave Sexton > > "Ben R." <benr@newsgroup.nospam> wrote in message news:AF6EED6C-7C1C-4C7B-93D2-2A01231C7552@microsoft.com... > > Hi, > > > > I learned that for my.sttings, I can pull an entry by name, but can I use > > reflection to load a varaible? Example > > > > void dosomething(string variablename) > > // note: value passed in for variable name is "foo" > > int foo=1 > > int bar=2 > > > > messagebox.show(reflectionhere(variablename)); > > > > I want 1 to show up. > > > > Is this possible? Is this what late binding is? There are circumstances > > where it'd be nice to construct a string which will represent a varaible name > > that I'd like to use. > > > > Thank you... > > > > -Ben > > > > > > > > > Hi Ben,
If your variables are all integers (or any of the supported base Types for Enums) then use an Enum as in my second example. Avoid the switch by casting the specified enum value to its base Type and assign each Enum constant the appropriate value: enum DoSomethingChoice { Foo = 1, Bar = 2 } void DoSomething(DoSomethingChoice choice) { int value = (int) choice; MessageBox.Show(value.ToString()); } If your variables are other Types such as strings or complex Types then you should use the switch statement. If you have a lot of variables then you might want to think of a better design. You could store the data in a Hashtable keyed by the DoSomethingChoice enum, for example. You could also expand the method into a more OOP design so that the argument passed to the method is a custom object that encapsulates all of the data that the method might require. -- Show quoteDave Sexton "Ben R." <benr@newsgroup.nospam> wrote in message news:96B6BD0B-C7DE-4810-A577-40ADBB0C0B08@microsoft.com... > Hey Dave, > > Thanks for the response. I was thinking about putting in the switching logic > you suggested, but I'm wondering if this can be avoided. I'm considering a > situation where I have many different variables that could be used, instead > of just 2. It seems silly to have to write switching logic for each variable > when each case is doing something very similar: going from string "x" to > variable x. > > Is there any way you know of to accomplish this without explicit switching > logic? > > -Ben > > "Dave Sexton" wrote: > >> Hi Ben, >> >> No reflection or binding needed: >> >> string text = null; >> >> switch (variableName) >> { >> case "foo": >> text = foo.ToString(); >> break; >> case "bar": >> text = bar.ToString(); >> break; >> } >> >> MessageBox.Show(text); >> >> >> I'm not sure it's such a good idea to pass in the name of a local variable though. An Enum would be appropriate here instead: >> >> enum DoSomethingChoice >> { >> Foo, >> Bar >> } >> >> class FooBarChoiceTest >> { >> int foo = 1, bar = 2; >> >> void DoSomething(DoSomethingChoice choice) >> { >> string text = null; >> >> switch (choice) >> { >> case DoSomethingChoice.Foo: >> text = foo.ToString(); >> break; >> case DoSomethingChoice.Bar: >> text = bar.ToString(); >> break; >> default: >> throw new System.ComponentModel.InvalidEnumArgumentException( >> "choice", (int) choice, typeof(DoSomethingChoice)); >> } >> >> MessageBox.Show(text); >> } >> } >> >> -- >> Dave Sexton >> >> "Ben R." <benr@newsgroup.nospam> wrote in message news:AF6EED6C-7C1C-4C7B-93D2-2A01231C7552@microsoft.com... >> > Hi, >> > >> > I learned that for my.sttings, I can pull an entry by name, but can I use >> > reflection to load a varaible? Example >> > >> > void dosomething(string variablename) >> > // note: value passed in for variable name is "foo" >> > int foo=1 >> > int bar=2 >> > >> > messagebox.show(reflectionhere(variablename)); >> > >> > I want 1 to show up. >> > >> > Is this possible? Is this what late binding is? There are circumstances >> > where it'd be nice to construct a string which will represent a varaible name >> > that I'd like to use. >> > >> > Thank you... >> > >> > -Ben >> > >> > >> > >> >> >> Hi Ben,
It's possible to use Reflection to get/set the variable value: public int foo = 1; public int bar = 2; private int privateFoo = 1; public void dosomething(string variablename) { Type t = this.GetType(); FieldInfo fi = t.GetField("privateFoo", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public); Console.WriteLine(fi.GetValue(this)); } From: #Early and Late Binding http://msdn2.microsoft.com/en-us/library/0tcf61s1.aspx The Visual Basic compiler performs a process called binding when an object is assigned to an object variable. An object is early bound when it is assigned to a variable declared to be of a specific object type. Early bound objects allow the compiler to allocate memory and perform other optimizations before an application executes. By contrast, an object is late bound when it is assigned to a variable declared to be of type Object. Objects of this type can hold references to any object, but lack many of the advantages of early-bound objects. C# does not handle late binding. For late binding related information, please refer to: #Dynamically Loading and Using Types http://msdn2.microsoft.com/en-us/library/k3a58006.aspx Please reply here to let us know whether or not you need further information. Thank you. Sincerely, Walter Wang (waw***@online.microsoft.com, remove 'online.') Microsoft Online Community Support ================================================== Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif ications. If you are using Outlook Express, please make sure you clear the check box "Tools/Options/Read: Get 300 headers at a time" to see your reply promptly. Note: The MSDN Managed Newsgroup support offering is for non-urgent issues where an initial response from the community or a Microsoft Support Engineer within 1 business day is acceptable. Please note that each follow up response may take approximately 2 business days as the support professional working with you may need further investigation to reach the most efficient resolution. The offering is not appropriate for situations that require urgent, real-time or phone-based interactions or complex project analysis and dump analysis issues. Issues of this nature are best handled working with a dedicated Microsoft Support Engineer by contacting Microsoft Customer Support Services (CSS) at http://msdn.microsoft.com/subscriptions/support/default.aspx. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights. Walter,
Thanks! This is great info. You've also inspired me to dig deeper into custom binding.. -Ben Show quote "Walter Wang [MSFT]" wrote: > Hi Ben, > > It's possible to use Reflection to get/set the variable value: > > public int foo = 1; > public int bar = 2; > private int privateFoo = 1; > > public void dosomething(string variablename) > { > Type t = this.GetType(); > FieldInfo fi = t.GetField("privateFoo", BindingFlags.Instance | > BindingFlags.NonPublic | BindingFlags.Public); > Console.WriteLine(fi.GetValue(this)); > } > > From: > > #Early and Late Binding > http://msdn2.microsoft.com/en-us/library/0tcf61s1.aspx > > The Visual Basic compiler performs a process called binding when an object > is assigned to an object variable. An object is early bound when it is > assigned to a variable declared to be of a specific object type. Early > bound objects allow the compiler to allocate memory and perform other > optimizations before an application executes. > > By contrast, an object is late bound when it is assigned to a variable > declared to be of type Object. Objects of this type can hold references to > any object, but lack many of the advantages of early-bound objects. > > C# does not handle late binding. > > For late binding related information, please refer to: > > #Dynamically Loading and Using Types > http://msdn2.microsoft.com/en-us/library/k3a58006.aspx > > Please reply here to let us know whether or not you need further > information. Thank you. > > > Sincerely, > Walter Wang (waw***@online.microsoft.com, remove 'online.') > Microsoft Online Community Support > > ================================================== > Get notification to my posts through email? Please refer to > http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif > ications. If you are using Outlook Express, please make sure you clear the > check box "Tools/Options/Read: Get 300 headers at a time" to see your reply > promptly. > > Note: The MSDN Managed Newsgroup support offering is for non-urgent issues > where an initial response from the community or a Microsoft Support > Engineer within 1 business day is acceptable. Please note that each follow > up response may take approximately 2 business days as the support > professional working with you may need further investigation to reach the > most efficient resolution. The offering is not appropriate for situations > that require urgent, real-time or phone-based interactions or complex > project analysis and dump analysis issues. Issues of this nature are best > handled working with a dedicated Microsoft Support Engineer by contacting > Microsoft Customer Support Services (CSS) at > http://msdn.microsoft.com/subscriptions/support/default.aspx. > ================================================== > > This posting is provided "AS IS" with no warranties, and confers no rights. > > Hi Ben,
I would be more happier if you had replied earlier, :) Just kidding, anyway, thank you for letting me know that the suggestion helped. Have a nice day! Regards, Walter Wang (waw***@online.microsoft.com, remove 'online.') Microsoft Online Community Support ================================================== When responding to posts, please "Reply to Group" via your newsreader so that others may learn and benefit from your issue. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights.  |
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