Question

I’m trying to figure out if it is possible to instantiate and invoke a delegate by name, rather than explicitly. I think the code belows explains it fairly well….I want to accept a function name, and then instantiate the delegate based on that. In the example I use a select case, but I want to eliminate that and just use the methodName argument itself.

Respectfully…please avoid the urge to tell me this is insane and I should be taking some entirely different approach to this. 🙂

    Private Delegate Sub myDelegate()        Private Sub myDelegate_Implementation1()         'Some code     End Sub     Private Sub myDelegate_Implementation2()         'Some code     End Sub      Public Sub InvokeMethod(ByVal methodName As String)         Dim func As myDelegate = Nothing         '??? HOW TO GET RID OF THIS SELECT CASE BLOCK?:         Select Case methodName             Case 'myDelegate_Implementation1'                 func = AddressOf myDelegate_Implementation1             Case 'myDelegate_Implementation2'                 func = AddressOf myDelegate_Implementation2         End Select         func.Invoke()     End Sub 

Thanks Keith, exactly what I was looking for. (BFree’s approach would work as well in most circumstances though).

Here’s the working code in VB:

Public Delegate Sub xxxDelegate()  Sub xxxAnImplementation()  End Sub  Sub zzzDoIt(ByVal xxxImplementerName As String)     Dim theDelegate As xxxDelegate = CType(System.Delegate.CreateDelegate(GetType(xxxDelegate), Me, xxxImplementerName), xxxDelegate)     theDelegate.Invoke() End Sub  Private Sub LoadFunctions()     Dim thisClass As Type = Type.GetType(Me.GetType.BaseType.FullName.ToString)     For Each method As MethodInfo In thisClass.GetMethods(System.Reflection.BindingFlags.DeclaredOnly)         If 1 = 1 OrElse method.Name.Substring(0, 3) = 'Get' Then             Me.ddlCodeSamples.Items.Add(method.Name)         End If     Next End Sub 

Answer 1

If you have a delegate for the method you can also do this:

public delegate void MethodDelegate( ... ) ...  //create the delegate we expect (MethodDelegate) Delegate.CreateDelegate(     typeof( MethodDelegate ), this, 'methodName', true ); 

C#, I know, but the similar will work in VB.

Normally I’d go with @BFree’s answer, but this works well when working with event driven reflection – I think this will be slightly quicker if calling the result delegate lots of times.