Coding a delegate in C#

Question

  I use a third party dll which returns information to my code in VB by way of a function in my code which I provide the dll with the address :
            result = wLib.Initialize(Key, AddressOf ApiGuiCallback)
wLib is the third party dll, ApiGuiCallback is my function to receive the data from the dll.

  My ApiGuiCallback Function is coded as such:
Private Function ApiGuiCallback(ByVal state As UInteger, _
ByVal msg As GuiMessage, ByVal buff As ImageInfo) As Integer
 
   How do I code this in C# so that the dll will execute my ApiGuiCallback function upon it's completion?

Denny