Control.HelpRequested Event

Occurs when the user requests help for a control.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

'Declaration
Public Event HelpRequested As HelpEventHandler
'Usage
Dim instance As Control
Dim handler As HelpEventHandler

AddHandler instance.HelpRequested, handler

/** @event */
public void add_HelpRequested (HelpEventHandler value)

/** @event */
public void remove_HelpRequested (HelpEventHandler value)

JScript supports the use of events, but not the declaration of new ones.

The HelpRequested event is commonly raised when the user presses the F1 key or an associated context-sensitive help button is clicked.

For more information about handling events, see Consuming Events.

The following code example demonstrates handling the HelpRequested event to display custom Help content on a form containing four address fields. The HelpRequested event is raised either by pressing the F1 key with the focus in an address field, or by the using the context-sensitive Help button and clicking the Help cursor on an address field. The Handled property is set to true to indicate that the HelpRequested event is handled. The example also demonstrates storing the Help text in the Control.Tag property.

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Public Class Form1
    Inherits System.Windows.Forms.Form
    Private WithEvents addressTextBox As System.Windows.Forms.TextBox
    Private WithEvents label2 As System.Windows.Forms.Label
    Private WithEvents cityTextBox As System.Windows.Forms.TextBox
    Private WithEvents label3 As System.Windows.Forms.Label
    Private WithEvents stateTextBox As System.Windows.Forms.TextBox
    Private WithEvents zipTextBox As System.Windows.Forms.TextBox
    Private WithEvents helpLabel As System.Windows.Forms.Label

    <STAThread()> _
    Shared Sub Main()
        Application.Run(New Form1)
    End Sub 'Main

    Public Sub New()
        Me.addressTextBox = New System.Windows.Forms.TextBox
        Me.helpLabel = New System.Windows.Forms.Label
        Me.label2 = New System.Windows.Forms.Label
        Me.cityTextBox = New System.Windows.Forms.TextBox
        Me.label3 = New System.Windows.Forms.Label
        Me.stateTextBox = New System.Windows.Forms.TextBox
        Me.zipTextBox = New System.Windows.Forms.TextBox

        ' Help Label
        Me.helpLabel.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D
        Me.helpLabel.Location = New System.Drawing.Point(8, 80)
        Me.helpLabel.Size = New System.Drawing.Size(272, 72)
        Me.helpLabel.Text = "Click on any control to give it focus, and then " & _
            "press F1 to display help for that" + " control.  Alternately, you can " & _
            "click the help button at the top of the dialog and then click on a control."

        ' Address Label
        Me.label2.Location = New System.Drawing.Point(16, 8)
        Me.label2.Size = New System.Drawing.Size(100, 16)
        Me.label2.Text = "Address:"

        ' Comma Label
        Me.label3.Location = New System.Drawing.Point(136, 56)
        Me.label3.Size = New System.Drawing.Size(16, 16)
        Me.label3.Text = ","

        ' Address TextBox
        Me.addressTextBox.Location = New System.Drawing.Point(16, 24)
        Me.addressTextBox.Size = New System.Drawing.Size(264, 20)
        Me.addressTextBox.TabIndex = 0
        Me.addressTextBox.Tag = "Enter the stree address in this text box."
        Me.addressTextBox.Text = ""

        ' City TextBox
        Me.cityTextBox.Location = New System.Drawing.Point(16, 48)
        Me.cityTextBox.Size = New System.Drawing.Size(120, 20)
        Me.cityTextBox.TabIndex = 3
        Me.cityTextBox.Tag = "Enter the city here."
        Me.cityTextBox.Text = ""

        ' State TextBox
        Me.stateTextBox.Location = New System.Drawing.Point(152, 48)
        Me.stateTextBox.MaxLength = 2
        Me.stateTextBox.Size = New System.Drawing.Size(32, 20)
        Me.stateTextBox.TabIndex = 5
        Me.stateTextBox.Tag = "Enter the state in this text box."
        Me.stateTextBox.Text = ""

        ' Zip TextBox
        Me.zipTextBox.Location = New System.Drawing.Point(192, 48)
        Me.zipTextBox.Size = New System.Drawing.Size(88, 20)
        Me.zipTextBox.TabIndex = 6
        Me.zipTextBox.Tag = "Enter the zip code here."
        Me.zipTextBox.Text = ""

        ' Set up how the form should be displayed and add the controls to the form.
        Me.ClientSize = New System.Drawing.Size(292, 160)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.zipTextBox, _
                                Me.stateTextBox, Me.label3, Me.cityTextBox, _
                                Me.label2, Me.helpLabel, Me.addressTextBox})
        Me.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog
        Me.HelpButton = True
        Me.MaximizeBox = False
        Me.MinimizeBox = False
        Me.Text = "Help Event Demonstration"
    End Sub 'New

    Private Sub textBox_HelpRequested(ByVal sender As Object, ByVal hlpevent As System.Windows.Forms.HelpEventArgs) Handles addressTextBox.HelpRequested, cityTextBox.HelpRequested, stateTextBox.HelpRequested, zipTextBox.HelpRequested
        ' This event is raised when the F1 key is pressed or the
        ' Help cursor is clicked on any of the address fields.
        ' The Help text for the field is in the control's
        ' Tag property. It is retrieved and displayed in the label.

        Dim requestingControl As Control = CType(sender, Control)
        helpLabel.Text = CStr(requestingControl.Tag)
        hlpevent.Handled = True

    End Sub 'textBox_HelpRequested
End Class 'Form1

import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;

public class Form1 extends System.Windows.Forms.Form
{
    private System.Windows.Forms.TextBox addressTextBox;
    private System.Windows.Forms.Label label2;
    private System.Windows.Forms.TextBox cityTextBox;
    private System.Windows.Forms.Label label3;
    private System.Windows.Forms.TextBox stateTextBox;
    private System.Windows.Forms.TextBox zipTextBox;
    private System.Windows.Forms.Label helpLabel;

    /** @attribute STAThread()
     */
    public static void main(String[] args)
    {
        Application.Run(new Form1());
    } //main

    public Form1()
    {
        this.addressTextBox = new System.Windows.Forms.TextBox();
        this.helpLabel = new System.Windows.Forms.Label();
        this.label2 = new System.Windows.Forms.Label();
        this.cityTextBox = new System.Windows.Forms.TextBox();
        this.label3 = new System.Windows.Forms.Label();
        this.stateTextBox = new System.Windows.Forms.TextBox();
        this.zipTextBox = new System.Windows.Forms.TextBox();
        // Help Label
        this.helpLabel.set_BorderStyle(
            System.Windows.Forms.BorderStyle.Fixed3D);
        this.helpLabel.set_Location(new System.Drawing.Point(8, 80));
        this.helpLabel.set_Size(new System.Drawing.Size(272, 72));
        this.helpLabel.set_Text("Click on any control to give it focus, " 
            + "and then press F1 to display help for that control.  " 
            + "Alternately, you can click the help button at the top of " 
            + "the dialog and then click on a control.");
        // Address Label
        this.label2.set_Location(new System.Drawing.Point(16, 8));
        this.label2.set_Size(new System.Drawing.Size(100, 16));
        this.label2.set_Text("Address:");
        // Comma Label
        this.label3.set_Location(new System.Drawing.Point(136, 56));
        this.label3.set_Size(new System.Drawing.Size(16, 16));
        this.label3.set_Text(",");
        // Address TextBox
        this.addressTextBox.set_Location(new System.Drawing.Point(16, 24));
        this.addressTextBox.set_Size(new System.Drawing.Size(264, 20));
        this.addressTextBox.set_TabIndex(0);
        this.addressTextBox.set_Tag("Enter the street address " 
            + "in this text box.");
        this.addressTextBox.set_Text("");
        this.addressTextBox.add_HelpRequested(
            new System.Windows.Forms.HelpEventHandler(
            this.TextBox_HelpRequested));
        // City TextBox
        this.cityTextBox.set_Location(new System.Drawing.Point(16, 48));
        this.cityTextBox.set_Size(new System.Drawing.Size(120, 20));
        this.cityTextBox.set_TabIndex(3);
        this.cityTextBox.set_Tag("Enter the city here.");
        this.cityTextBox.set_Text("");
        this.cityTextBox.add_HelpRequested(
            new System.Windows.Forms.HelpEventHandler(
            this.TextBox_HelpRequested));
        // State TextBox
        this.stateTextBox.set_Location(new System.Drawing.Point(152, 48));
        this.stateTextBox.set_MaxLength(2);
        this.stateTextBox.set_Size(new System.Drawing.Size(32, 20));
        this.stateTextBox.set_TabIndex(5);
        this.stateTextBox.set_Tag("Enter the state in this text box.");
        this.stateTextBox.set_Text("");
        this.stateTextBox.add_HelpRequested(
            new System.Windows.Forms.HelpEventHandler(
            this.TextBox_HelpRequested));
        // Zip TextBox
        this.zipTextBox.set_Location(new System.Drawing.Point(192, 48));
        this.zipTextBox.set_Name("zipTextBox");
        this.zipTextBox.set_Size(new System.Drawing.Size(88, 20));
        this.zipTextBox.set_TabIndex(6);
        this.zipTextBox.set_Tag("Enter the zip code here.");
        this.zipTextBox.set_Text("");
        this.zipTextBox.add_HelpRequested(
            new System.Windows.Forms.HelpEventHandler(
            this.TextBox_HelpRequested));
        // Set up how the form should be displayed and add the controls 
        // to the form.
        this.set_ClientSize(new System.Drawing.Size(292, 160));
        this.get_Controls().AddRange(new System.Windows.Forms.Control[] { 
            this.zipTextBox, this.stateTextBox, this.label3, this.cityTextBox, 
            this.label2, this.helpLabel, this.addressTextBox });

        this.set_FormBorderStyle(
            System.Windows.Forms.FormBorderStyle.FixedDialog);
        this.set_HelpButton(true);
        this.set_MaximizeBox(false);
        this.set_MinimizeBox(false);
        this.set_Text("Help Event Demonstration");
    } //Form1

    private void TextBox_HelpRequested(Object sender, 
        System.Windows.Forms.HelpEventArgs hlpEvent)
    {
        // This event is raised when the F1 key is pressed or the
        // Help cursor is clicked on any of the address fields.
        // The Help text for the field is in the control's
        // Tag property. It is retrieved and displayed in the label.
        Control requestingControl = (Control)sender;
        helpLabel.set_Text((String)requestingControl.get_Tag());
        hlpEvent.set_Handled(true);
    } //TextBox_HelpRequested
} //Form1

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0

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