Add and remove event handler : Event « Event « VB.Net Tutorial

1. VB.Net Tutorial
2. Event
3. Event

Imports System.Windows.Forms

public class AddRemoveEventHandler
   public Shared Sub Main
        Application.Run(New Form1)
   End Sub
End class


Public Class Form1

    Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
        If RadioButton1.Checked Then
            AddHandler Button1.Click, AddressOf ButtonHandler1
        Else
            RemoveHandler Button1.Click, AddressOf ButtonHandler1
        End If
    End Sub


    Private Sub RadioButton2_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton2.CheckedChanged
        If RadioButton2.Checked Then
            AddHandler Button1.Click, AddressOf ButtonHandler2
        Else
            RemoveHandler Button1.Click, AddressOf ButtonHandler2
        End If
    End Sub

    Private Sub ButtonHandler1(ByVal sender As System.Object, ByVal e As System.EventArgs)
        MessageBox.Show("ButtonHandler1")
    End Sub
    Private Sub ButtonHandler2(ByVal sender As System.Object, ByVal e As System.EventArgs)
        MessageBox.Show("ButtonHandler2")
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        RadioButton1.Checked = True
    End Sub

End Class
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Public Class Form1
    Inherits System.Windows.Forms.Form

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing AndAlso components IsNot Nothing Then
            components.Dispose()
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.RadioButton1 = New System.Windows.Forms.RadioButton
        Me.RadioButton2 = New System.Windows.Forms.RadioButton
        Me.Button1 = New System.Windows.Forms.Button
        Me.SuspendLayout()
        '
        'RadioButton1
        '
        Me.RadioButton1.AutoSize = True
        Me.RadioButton1.Location = New System.Drawing.Point(8, 8)
        Me.RadioButton1.Name = "RadioButton1"
        Me.RadioButton1.Size = New System.Drawing.Size(99, 17)
        Me.RadioButton1.TabIndex = 0
        Me.RadioButton1.Text = "ButtonHandler1"
        Me.RadioButton1.UseVisualStyleBackColor = True
        '
        'RadioButton2
        '
        Me.RadioButton2.AutoSize = True
        Me.RadioButton2.Location = New System.Drawing.Point(8, 40)
        Me.RadioButton2.Name = "RadioButton2"
        Me.RadioButton2.Size = New System.Drawing.Size(99, 17)
        Me.RadioButton2.TabIndex = 1
        Me.RadioButton2.Text = "ButtonHandler2"
        Me.RadioButton2.UseVisualStyleBackColor = True
        '
        'Button1
        '
        Me.Button1.Location = New System.Drawing.Point(152, 16)
        Me.Button1.Name = "Button1"
        Me.Button1.Size = New System.Drawing.Size(75, 23)
        Me.Button1.TabIndex = 2
        Me.Button1.Text = "Button1"
        Me.Button1.UseVisualStyleBackColor = True
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.Add(Me.Button1)
        Me.Controls.Add(Me.RadioButton2)
        Me.Controls.Add(Me.RadioButton1)
        Me.Name = "Form1"
        Me.Text = "AddRemoveHandler"
        Me.ResumeLayout(False)
        Me.PerformLayout()

    End Sub
    Friend WithEvents RadioButton1 As System.Windows.Forms.RadioButton
    Friend WithEvents RadioButton2 As System.Windows.Forms.RadioButton
    Friend WithEvents Button1 As System.Windows.Forms.Button

End Class

11.1.Event
	11.1.1.	Raise Events
	11.1.2.	Multiple Event Handler
	11.1.3.	Event handler
	11.1.4.	Subclass EventArgs to create your own event arguments
	11.1.5.	Inherit Event
	11.1.6.	Custom event handler
	11.1.7.	WithEvents and Event method
	11.1.8.	Add and remove event handler
	11.1.9.	Handle events from more than one components
	11.1.10.	Add, remove event handler to/from ToggleButton
	11.1.11.	Use one method to handle more than one RadioButton click event
	11.1.12.	Get event sender type
	11.1.13.	Instantiating the Action<(Of <(T>)>) delegate rather than explicitly defining a new delegate and assigning a named method