HelpEventHandler Delegado

Definición

Espacio de nombres:

System.Windows.Forms

Ensamblado:

System.Windows.Forms.dll

Representa el método que controlará el evento HelpRequested de Control.

public delegate void HelpEventHandler(System::Object ^ sender, HelpEventArgs ^ hlpevent);

public delegate void HelpEventHandler(object? sender, HelpEventArgs hlpevent);

type HelpEventHandler = delegate of obj * HelpEventArgs -> unit

Public Delegate Sub HelpEventHandler(sender As Object, hlpevent As HelpEventArgs)

Parámetros

sender

Object

Origen del evento.

hlpevent

HelpEventArgs

Objeto HelpEventArgs que contiene los datos del evento.

Ejemplos

En el ejemplo siguiente se muestra cómo controlar el HelpRequested evento para mostrar el contenido de la Ayuda personalizada en un formulario que contiene cuatro campos de dirección. El HelpRequested evento se genera presionando la tecla F1 con el foco en un campo de dirección o mediante el botón Ayuda contextual y haciendo clic en el cursor ayuda en un campo de dirección. La Handled propiedad se establece en true para indicar que se controla el HelpRequested evento. En el ejemplo también se muestra cómo almacenar el texto de ayuda en la Control.Tag propiedad .

#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
public ref class Form1: public System::Windows::Forms::Form
{
private:
   System::Windows::Forms::TextBox^ addressTextBox;
   System::Windows::Forms::Label ^ label2;
   System::Windows::Forms::TextBox^ cityTextBox;
   System::Windows::Forms::Label ^ label3;
   System::Windows::Forms::TextBox^ stateTextBox;
   System::Windows::Forms::TextBox^ zipTextBox;
   System::Windows::Forms::Label ^ helpLabel;

public:
   Form1()
   {
      this->addressTextBox = gcnew System::Windows::Forms::TextBox;
      this->helpLabel = gcnew System::Windows::Forms::Label;
      this->label2 = gcnew System::Windows::Forms::Label;
      this->cityTextBox = gcnew System::Windows::Forms::TextBox;
      this->label3 = gcnew System::Windows::Forms::Label;
      this->stateTextBox = gcnew System::Windows::Forms::TextBox;
      this->zipTextBox = gcnew System::Windows::Forms::TextBox;
      
      // Help Label
      this->helpLabel->BorderStyle = System::Windows::Forms::BorderStyle::Fixed3D;
      this->helpLabel->Location = System::Drawing::Point( 8, 80 );
      this->helpLabel->Size = System::Drawing::Size( 272, 72 );
      this->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
      this->label2->Location = System::Drawing::Point( 16, 8 );
      this->label2->Size = System::Drawing::Size( 100, 16 );
      this->label2->Text = "Address:";
      
      // Comma Label
      this->label3->Location = System::Drawing::Point( 136, 56 );
      this->label3->Size = System::Drawing::Size( 16, 16 );
      this->label3->Text = ", ";
      
      // Address TextBox
      this->addressTextBox->Location = System::Drawing::Point( 16, 24 );
      this->addressTextBox->Size = System::Drawing::Size( 264, 20 );
      this->addressTextBox->TabIndex = 0;
      this->addressTextBox->Tag = "Enter the street address in this text box.";
      this->addressTextBox->Text = "";
      this->addressTextBox->HelpRequested += gcnew System::Windows::Forms::HelpEventHandler( this, &Form1::textBox_HelpRequested );
      
      // City TextBox
      this->cityTextBox->Location = System::Drawing::Point( 16, 48 );
      this->cityTextBox->Size = System::Drawing::Size( 120, 20 );
      this->cityTextBox->TabIndex = 3;
      this->cityTextBox->Tag = "Enter the city here.";
      this->cityTextBox->Text = "";
      this->cityTextBox->HelpRequested += gcnew System::Windows::Forms::HelpEventHandler( this, &Form1::textBox_HelpRequested );
      
      // State TextBox
      this->stateTextBox->Location = System::Drawing::Point( 152, 48 );
      this->stateTextBox->MaxLength = 2;
      this->stateTextBox->Size = System::Drawing::Size( 32, 20 );
      this->stateTextBox->TabIndex = 5;
      this->stateTextBox->Tag = "Enter the state in this text box.";
      this->stateTextBox->Text = "";
      this->stateTextBox->HelpRequested += gcnew System::Windows::Forms::HelpEventHandler( this, &Form1::textBox_HelpRequested );
      
      // Zip TextBox
      this->zipTextBox->Location = System::Drawing::Point( 192, 48 );
      this->zipTextBox->Name = "zipTextBox";
      this->zipTextBox->Size = System::Drawing::Size( 88, 20 );
      this->zipTextBox->TabIndex = 6;
      this->zipTextBox->Tag = "Enter the zip code here.";
      this->zipTextBox->Text = "";
      this->zipTextBox->HelpRequested += gcnew System::Windows::Forms::HelpEventHandler( this, &Form1::textBox_HelpRequested );
      
      // Set up how the form should be displayed and add the controls to the form.
      this->ClientSize = System::Drawing::Size( 292, 160 );
      array<System::Windows::Forms::Control^>^temp0 = {this->zipTextBox,this->stateTextBox,this->label3,this->cityTextBox,this->label2,this->helpLabel,this->addressTextBox};
      this->Controls->AddRange( temp0 );
      this->FormBorderStyle = System::Windows::Forms::FormBorderStyle::FixedDialog;
      this->HelpButton = true;
      this->MaximizeBox = false;
      this->MinimizeBox = false;
      this->Text = "Help Event Demonstration";
   }


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 = dynamic_cast<Control^>(sender);
      helpLabel->Text = dynamic_cast<String^>(requestingControl->Tag);
      hlpevent->Handled = true;
   }

};


[STAThread]
int main()
{
   Application::Run( gcnew Form1 );
}

using System;
using System.Drawing;
using System.Windows.Forms;

public class Form1 : 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;

    [STAThread]
    static void Main() 
    {
        Application.Run(new Form1());
    }

    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.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
        this.helpLabel.Location = new System.Drawing.Point(8, 80);
        this.helpLabel.Size = new System.Drawing.Size(272, 72);
        this.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
        this.label2.Location = new System.Drawing.Point(16, 8);
        this.label2.Size = new System.Drawing.Size(100, 16);
        this.label2.Text = "Address:";

        // Comma Label
        this.label3.Location = new System.Drawing.Point(136, 56);
        this.label3.Size = new System.Drawing.Size(16, 16);
        this.label3.Text = ",";

        // Address TextBox
        this.addressTextBox.Location = new System.Drawing.Point(16, 24);
        this.addressTextBox.Size = new System.Drawing.Size(264, 20);
        this.addressTextBox.TabIndex = 0;
        this.addressTextBox.Tag = "Enter the street address in this text box.";
        this.addressTextBox.Text = "";
        this.addressTextBox.HelpRequested += new System.Windows.Forms.HelpEventHandler(this.textBox_HelpRequested);

        // City TextBox
        this.cityTextBox.Location = new System.Drawing.Point(16, 48);
        this.cityTextBox.Size = new System.Drawing.Size(120, 20);
        this.cityTextBox.TabIndex = 3;
        this.cityTextBox.Tag = "Enter the city here.";
        this.cityTextBox.Text = "";
        this.cityTextBox.HelpRequested += new System.Windows.Forms.HelpEventHandler(this.textBox_HelpRequested);

        // State TextBox
        this.stateTextBox.Location = new System.Drawing.Point(152, 48);
        this.stateTextBox.MaxLength = 2;
        this.stateTextBox.Size = new System.Drawing.Size(32, 20);
        this.stateTextBox.TabIndex = 5;
        this.stateTextBox.Tag = "Enter the state in this text box.";
        this.stateTextBox.Text = "";
        this.stateTextBox.HelpRequested += new System.Windows.Forms.HelpEventHandler(this.textBox_HelpRequested);

        // Zip TextBox
        this.zipTextBox.Location = new System.Drawing.Point(192, 48);
        this.zipTextBox.Name = "zipTextBox";
        this.zipTextBox.Size = new System.Drawing.Size(88, 20);
        this.zipTextBox.TabIndex = 6;
        this.zipTextBox.Tag = "Enter the zip code here.";
        this.zipTextBox.Text = "";
        this.zipTextBox.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.ClientSize = new System.Drawing.Size(292, 160);
        this.Controls.AddRange(new System.Windows.Forms.Control[] { this.zipTextBox, 
                                this.stateTextBox, this.label3, this.cityTextBox,  
                                this.label2, this.helpLabel, this.addressTextBox});

        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog;
        this.HelpButton = true;
        this.MaximizeBox = false;
        this.MinimizeBox = false;
        this.Text = "Help Event Demonstration";    
    }

    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.Text = (string)requestingControl.Tag;
        hlpevent.Handled = true;
    }
}

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

    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

    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
End Class

Comentarios

Cuando se crea un delegado HelpEventHandler, se identifica el método que controlará el evento. Para asociar el evento al controlador, se debe agregar una instancia del delegado al evento. Siempre que se produce el evento, se llama a su controlador, a menos que se quite el delegado. Para obtener más información sobre cómo controlar eventos con delegados, vea Control y generación de eventos.

Métodos de extensión

Consulte también

• HelpRequested
• HelpEventArgs