Reflection makes it easy to invoke a method (or assign a field or aproperty) by its name. For example, suppose you have the following classes:
Class Person Event PropertyChanged(ByVal propertyName As String, ByVal newValue As Object) Dim m_Name As String Property Name() As String Get Return m_Name End Get Set(ByVal Value As String) If Value <> m_Name Then m_Name = Value RaiseEvent PropertyChanged("Name", m_Name) End If End Set End PropertyEnd ClassHere’s how you can assign a Person’s Name and a Car’s Color throughreflection:
' this code assumes the following statement' Imports System.Reflection' create a Person objectDim pe As New Person()' note how you can create the array of arguments on the flype.GetType.InvokeMember("Name", BindingFlags.SetProperty, Nothing, pe, _ New Object() {"John"})However, setting up an event handler for an event of which you know just thename isn’t as immediate. These are the steps you need to follow:
1. Create an event handler that reflects the event syntax
2. Get the EventInfo object corresponding to the event in question
3. Create a delegate to local event handler by means of the Delegate.CreateDelegate method
4. call the EventInfo.AddEventHandler method to establish the connection
Remember to remove the event handler when you don’t need to receive eventsany longer. Here’s a complete example that uses the Person class, but it canbe easily adapted to other classes:
Module MainModule Sub Main ' create a Person object Dim pe As New Person() ' get a reference to the EventInfo for this object Dim peEv As EventInfo = pe.GetType.GetEvent("PropertyChanged") ' create a delegate to the local procedure Dim peDel As [Delegate] = [Delegate].CreateDelegate(peEv.EventHandlerType, _ Me, "PropertyChanged") ' make the local procedure a handler for the event peEv.AddEventHandler(pe, peDel) ' prove that it works pe.Name = "John" ' (always remove event handlers) peEv.RemoveEventHandler(pe, peDel) End Sub Private Sub PropertyChanged(ByVal propertyName As String, _ ByVal newValue As Object) Console.WriteLine("Property {0} has changed. The new value is {1}", _ propertyName, newValue) End SubEnd Module
