Possible to instantiate and invoke a delegate by name?
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
Solution
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.
OTHER TIPS
I won't fully answer question, because I'm not sure if what you're asking is possible. What IS possible though, through Reflection, is to Invoke a method given the Method name. IE:
string methodName = "MyMethod";
MethodInfo method = this.GetType().GetMethod(methodName);
method.Invoke(this, null);
Why not use a HashTable instead of a Select statement?
BFree's answer works;
My answer is just a suggestion;
Why not just pass an address of method to InvokeMethod instead of passing method name in string?
Module Module1
Sub Main()
InvokeMethod(AddressOf myDelegate_Implementation1)
InvokeMethod(AddressOf myDelegate_Implementation2)
End Sub
Public Delegate Sub myDelegate()
Private Sub myDelegate_Implementation1()
Console.WriteLine("myDelegate_Implementation1")
End Sub
Private Sub myDelegate_Implementation2()
Console.WriteLine("myDelegate_Implementation2")
End Sub
Public Sub InvokeMethod(ByVal func As myDelegate)
func()
End Sub
End Module