Delegate.GetInvocationList Method

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Source:

Delegate.cs

Returns the invocation list of the delegate.

public:
 virtual cli::array <Delegate ^> ^ GetInvocationList();

public virtual Delegate[] GetInvocationList ();

abstract member GetInvocationList : unit -> Delegate[]
override this.GetInvocationList : unit -> Delegate[]

Public Overridable Function GetInvocationList () As Delegate()

Returns

Delegate[]

An array of delegates representing the invocation list of the current delegate.

Examples

The following example assigns three methods to a delegate. It then calls the GetInvocationList method to get a total count of the methods assigned to the delegate, to execute the delegates in reverse order, and to execute the methods whose name do not include the substring "File".

using System;
using System.IO;
using System.Reflection;
using System.Windows.Forms;

public class Example
{
   public static void Main()
   {
      Action<String> outputMessage = null;
      outputMessage += Console.WriteLine;
      outputMessage += OutputToFile;
      outputMessage += ShowMessageBox;

//       Dim output1 As Action(Of String) = AddressOf Console.WriteLine
//       Dim output2 As Action(Of String) = AddressOf OutputToFile
//       Dim output3 As Action(Of String) = AddressOf MessageBox.Show
//
//       outputMessage = [Delegate].Combine( { output1, output2, output3 } )
      Console.WriteLine("Invocation list has {0} methods.",
                        outputMessage.GetInvocationList().Length);

      // Invoke delegates normally.
      outputMessage("Hello there!");
      Console.WriteLine("Press <Enter> to continue...");
      Console.ReadLine();

      // Invoke each delegate in the invocation list in reverse order.
      for (int ctr = outputMessage.GetInvocationList().Length - 1; ctr >= 0; ctr--) {
         var outputMsg = outputMessage.GetInvocationList()[ctr];
         outputMsg.DynamicInvoke("Greetings and salutations!");
      }
      Console.WriteLine("Press <Enter> to continue...");
      Console.ReadLine();

      // Invoke each delegate that doesn't write to a file.
      for (int ctr = 0; ctr < outputMessage.GetInvocationList().Length; ctr++) {
         var outputMsg = outputMessage.GetInvocationList()[ctr];
         if (!outputMsg.GetMethodInfo().Name.Contains("File"))
            outputMsg.DynamicInvoke( new String[] { "Hi!" } );
      }
   }

   private static void OutputToFile(String s)
   {
      var sw = new StreamWriter(@".\output.txt");
      sw.WriteLine(s);
      sw.Close();
   }

   private static void ShowMessageBox(String s)
   {
      MessageBox.Show(s);
   }
}

open System
open System.IO
open System.Reflection
open System.Windows.Forms

let outputToFile (s: string) =
    use sw = new StreamWriter(@".\output.txt")
    sw.WriteLine s

let showMessageBox s =
    MessageBox.Show s |> ignore

let outputMessage =
    Delegate.Combine(
        Action<string>(Console.WriteLine),
        Action<string>(outputToFile),
        Action<string>(showMessageBox))
    :?> Action<string>

printfn $"Invocation list has {outputMessage.GetInvocationList().Length} methods."

// Invoke delegates normally.
outputMessage.Invoke "Hello there!"
printfn "Press <Enter> to continue..."
stdin.ReadLine() |> ignore

// Invoke each delegate in the invocation list in reverse order.
for i = outputMessage.GetInvocationList().Length - 1 downto 0 do
    let outputMsg = outputMessage.GetInvocationList()[i]
    outputMsg.DynamicInvoke "Greetings and salutations!"
    |> ignore

printfn "Press <Enter> to continue..."
stdin.ReadLine() |> ignore

// Invoke each delegate that doesn't write to a file.
for i = 0 to outputMessage.GetInvocationList().Length - 1 do
    let outputMsg = outputMessage.GetInvocationList()[i]
    if not (outputMsg.GetMethodInfo().Name.Contains "File") then
        outputMsg.DynamicInvoke "Hi!"
        |> ignore

Imports System.IO
Imports System.Reflection
Imports System.Windows.Forms

Module Example
   Public outputMessage As Action(Of String)
   
   Public Sub Main()
      Dim output1 As Action(Of String) = AddressOf Console.WriteLine
      Dim output2 As Action(Of String) = AddressOf OutputToFile 
      Dim output3 As Action(Of String) = AddressOf MessageBox.Show
      
      outputMessage = [Delegate].Combine( { output1, output2, output3 } )
      Console.WriteLine("Invocation list has {0} methods.", 
                        outputMessage.GetInvocationList().Count)

      ' Invoke delegates normally.
      outputMessage("Hello there!")
      Console.WriteLine("Press <Enter> to continue...")
      Console.ReadLine()
      
      ' Invoke each delegate in the invocation list in reverse order.
      For ctr As Integer = outputMessage.GetInvocationList().Count - 1 To 0 Step -1
          Dim outputMsg = outputMessage.GetInvocationList(ctr)
          outputMsg.DynamicInvoke("Greetings and salutations!")
      Next
      Console.WriteLine("Press <Enter> to continue...")
      Console.ReadLine()
      
      ' Invoke each delegate that doesn't write to a file.
      For ctr As Integer = 0 To outputMessage.GetInvocationList().Count - 1 
         Dim outputMsg = outputMessage.GetInvocationList(ctr)
         If Not outputMsg.GetMethodInfo().Name.Contains("File") Then
            outputMsg.DynamicInvoke( { "Hi!" } )
         End If
      Next
   End Sub
   
   Private Sub OutputToFile(s As String)
      Dim sw As New StreamWriter(".\output.txt")
      sw.WriteLine(s)
      sw.Close()
   End Sub
End Module

Remarks

Each delegate in the array represents exactly one method.

The order of the delegates in the array is the same order in which the current delegate invokes the methods that those delegates represent.