TechNet Wiki v2

How to access a method via its declaration name using reflection

I could spend a million words explaining it, or you could look at the code.

I encountered an interesting forum post where the person was storing the event-handler-name in a database as a string,for certain events. They needed a way of identifying(from a string) which method to assign to their object's events.

I created the following example that uses reflection to identify the correct routine by accessing its MethodInfo.Name property, later it converts this methodinfo into a delegate, and then into an eventhandler. It then can be dynamically added as the event handler for a controls event.

Keep in mind, as with coding always, if not used right, you will of course get errors.

Create a new test project
Double-Click Form1
Delete all code you see there.
Paste the following code into form1

'Option Strict is always recommended

Option Strict On

'Import Reflection

Imports System.Reflection

Public Class


Form1

'Create a menustrip for the form

WithEvents MenuStrip1 As New


MenuStrip

With


{.Parent =

Me}

'create a button to test our adder

WithEvents Button1 As New


Button

With


{.Parent =

Me, .Top = 100}

'Create a new instance of the MyMethods Class

Dim ObjectAdder As New


MyMethods

'Be sure to create a matching button for this button event

Private Sub


Button1_Click(

ByVal


sender

As


System.

Object

ByVal

As


System.EventArgs)

Handles Button1.Click

'Call the AddMenuItem sub from your instan style="color:#006699;font-weight:bold;">Private Sub


Button1_Click(

ByVal


sender

'


        'Tell the AddMenuItem method the name of your menustrip, the caption of the menuitem, and the name of the sub

        'in the MyMethods class that you want to become its event handler
        ObjectAdder.AddMenuItem(Me.MenuStrip1,
"Are You Out There???",
"SubC")
    End
Sub
End
Class



Add a new class to your project. 
Delete the default code from the new class 
Paste the following code into the new class 


Option
Strict On
Public
Class 
MyMethods
    'Pre-Defined Subs
    Public
Sub 
SubA(ByVal 
sender As 
Object, ByVal
e As
EventArgs)
        MsgBox("Hello, I am SubA, and I am your dynamic event handler.")
    End
Sub
    Public
Sub 
SubB(ByVal 
sender As 
Object, ByVal
e As
EventArgs)
        MsgBox("Hello, I am SubB, and I am your dynamic event handler.")
    End
Sub
    Public
Sub 
SubC(ByVal 
sender As 
Object, ByVal
e As
EventArgs)
        MsgBox("Hello, I am SubC, and I am your dynamic event handler.")
    End
Sub
    Public
Sub 
SubD(ByVal 
sender As 
Object, ByVal
e As
EventArgs)
        MsgBox("Hello, I am SubD, and I am your dynamic event handler.")
    End
Sub
    Public
Sub 
AddMenuItem(ByVal 
Menu As 
MenuStrip, ByVal 
MenuText As 
String, ByVal
MethodName As
String)
        'Create the new toolstripbutton
        Dim
ToolStripButton As
New 
ToolStripButton
        'Set the toolstrip button's caption
        ToolStripButton.Text = MenuText
        'Iterate through a collection of each methodinfo in the MyMethods class, using reflection
        For
Each 
Method As 
MethodInfo In 
GetType(MyMethods).GetMethods
            'If we find one with a name that matches the ssp;       'Iterate through a collection of each methodinfo in the MyMethods class, using reflection
        

            'then we create an event handler from the methodinfo
            If
Method.Name = MethodName Then
                'Add that handler to the toolstripbutton click event
                AddHandler
ToolStripButton.Click, EventHandlerFromMI(Method)
                'end iteration
                Exit
For
            End
If
        Next
        'add the toolstrip item to the specified menu
        Menu.Items.Add(ToolStripButton)
    End
Sub
    Public
Function 
EventHandlerFromMI(ByVal
MethodInfo As
System.Reflection.MethodInfo) As
EventHandler
        'Create a delegate from the methodinfo
        Dim
ConvertThisDelegate As
System.Delegate
= _
                System.Delegate.CreateDelegate(GetType(eventhandler),
Nothing, MethodInfo,
False)
        'convert the delegate into an eventhandler, and output it from the function
        Return
DirectCast(ConvertThisDelegate, EventHandler)
    End
Function
ght:bold;">Nothing, MethodInfo,
False)
        'convert the delegate into an eventhandleEnd
Class





Run the project and see the results speak for themself! 
References
Special thanks to John.

I was able to derive this neat trick using some information taught to me by John Anthony Oliver
MSDN Library - System.Reflection Namespace
MSDN 
MSDN Forums




Please check out my other Technet Wiki articles!

Reflection - Accessing A Method Via Its Declared Name String - Visual Basic.Net - TechNet Articles - United States (English) - TechNet Wiki

I created the following example that uses reflection to identify the correct routine by accessing its MethodInfo.Name property, later it converts this methodinfo into a delegate, and then into an eventhandler. It then can be dynamically added as the event handler for a controls event.

References