HtmlInputCheckBox.OnPreRender(EventArgs) Método

Referencia

Definición

Espacio de nombres:: System.Web.UI.HtmlControls

Ensamblado:: System.Web.dll

Importante

Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.

Genera el evento OnPreRender(EventArgs) y registra el control como un control que requiere controlar el postback.

protected:
 override void OnPreRender(EventArgs ^ e);

protected public:
 override void OnPreRender(EventArgs ^ e);

protected override void OnPreRender (EventArgs e);

protected internal override void OnPreRender (EventArgs e);

override this.OnPreRender : EventArgs -> unit

Protected Overrides Sub OnPreRender (e As EventArgs)

Protected Friend Overrides Sub OnPreRender (e As EventArgs)

Parámetros

e: EventArgs

EventArgs que contiene datos de eventos.

Ejemplos

En el ejemplo de código siguiente se muestra cómo invalidar el OnPreRender método en un control de servidor personalizado para que se agregue un Title atributo a cada HtmlInputCheckBox control.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>Custom HtmlInputCheckBox - OnPreRender - C# Example</title>
    <script runat="server">
      void Button1_Click(Object sender, EventArgs e)
      {
        Div1.InnerHtml = "";

        if(HtmlInputCheckBox1.Checked == true)
        {
          Div1.InnerHtml = "You like basketball. ";
        }

        if(HtmlInputCheckBox2.Checked == true)
        {
          Div1.InnerHtml += "You like football. ";
        }

        if(HtmlInputCheckBox3.Checked == true)
        {
          Div1.InnerHtml += "You like soccer. ";
        }
      }
    </script>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">
      <h3>Custom HtmlInputCheckBox - OnPreRender - C# Example</h3>
      <br />
      Enter Interests:<p>
      <aspSample:CustomHtmlInputCheckBoxOnPreRender
        id="HtmlInputCheckBox1"
        runat="server"
        type="checkbox" checked
        value="Basketball"> Basketball

      <aspSample:CustomHtmlInputCheckBoxOnPreRender
        id="HtmlInputCheckBox2"
        runat="server"
        type="checkbox"
        value="Football"> Football

      <aspSample:CustomHtmlInputCheckBoxOnPreRender
        id="HtmlInputCheckBox3"
        runat="server"
        type="checkbox"
        value="Soccer"> Soccer
      </p>
      <p>
      <input id="Button1"
        runat="server"
        type="button"
        value="Enter"
        onserverclick="Button1_Click"
        name="Button1" />
      </p>

      <div id="Div1" runat="server"
        style="DISPLAY: inline; WIDTH: 256px; HEIGHT: 15px" />
    </form>
  </body>
</html>

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls" Assembly="Samples.AspNet.VB" %>
<%@ Page Language="VB" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>Custom HtmlInputCheckBox - OnPreRender - Visual Basic Example</title>
    <script runat="server">
      Sub Button1_Click(sender As Object, e As EventArgs)
        Div1.InnerHtml = ""

        If HtmlInputCheckBox1.Checked = True Then
            Div1.InnerHtml = "You like basketball. "
        End If

        If HtmlInputCheckBox2.Checked = True Then
            Div1.InnerHtml += "You like football. "
        End If

        If HtmlInputCheckBox3.Checked = True Then
            Div1.InnerHtml += "You like soccer. "
        End If
      End Sub

    </script>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">
      <h3>Custom HtmlInputCheckBox - OnPreRender - Visual Basic Example</h3>
      <br />
      Enter Interests:<p>
      <aspSample:CustomHtmlInputCheckBoxOnPreRender
        id="HtmlInputCheckBox1"
        runat="server"
        type="checkbox" checked
        value="Basketball"> Basketball

      <aspSample:CustomHtmlInputCheckBoxOnPreRender
        id="HtmlInputCheckBox2"
        runat="server"
        type="checkbox"
        value="Football"> Football

      <aspSample:CustomHtmlInputCheckBoxOnPreRender
        id="HtmlInputCheckBox3"
        runat="server"
        type="checkbox"
        value="Soccer"> Soccer
      </p>
      <p>
      <input id="Button1"
        runat="server"
        type="button"
        value="Enter"
        onserverclick="Button1_Click"
        name="Button1" />
      </p>

      <br />
      <div id="Div1" runat="server"
        style="DISPLAY: inline; WIDTH: 256px; HEIGHT: 15px"
        ms_positioning="FlowLayout" />
    </form>
  </body>
</html>

using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public sealed class CustomHtmlInputCheckBoxOnPreRender : System.Web.UI.HtmlControls.HtmlInputCheckBox
    {
        protected override void OnPreRender(System.EventArgs e)
        {
            // Call the base class's OnPreRender method.
            base.OnPreRender(e);
            
            // Add a Title attribute to each HtmlInputCheckBox.
            this.Attributes.Add("title", "If you like " + this.Value + ", then select this check box.");
        }
    }
}

Imports System.Web
Imports System.Security.Permissions

Namespace Samples.AspNet.VB.Controls

    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public NotInheritable Class CustomHtmlInputCheckBoxOnPreRender
        Inherits System.Web.UI.HtmlControls.HtmlInputCheckBox

        Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs)

            ' Call the base class's OnPreRender method.
            MyBase.OnPreRender(e)

            ' Add a Title attribute to each HtmlInputCheckBox.
            Me.Attributes.Add("title", "If you like " + Me.Value + ", then select this check box.")
        End Sub
    End Class

End Namespace

Comentarios

El OnPreRender método invalida el método base OnPreRender . OnPreRender se usa principalmente por los desarrolladores de control.

Se aplica a

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