HtmlInputImage.OnPreRender(EventArgs) 方法

  • 参考

定义

命名空间:
System.Web.UI.HtmlControls
程序集:
System.Web.dll

引发 PreRender 事件。

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)

参数

e
EventArgs

包含事件数据的 EventArgs。

示例

下面的代码示例演示如何重写 方法， OnPreRender 使其始终显示不带边框的自定义 HtmlInputImage 服务器控件。

<%@ 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">
<script runat="server">
  void Page_Load(Object sender, EventArgs e)
  {    
    
    // Define the onclick attribute of custom HtmlInputImage.
    HtmlInputImage1.Attributes.Add("onclick", "alert('Hello client-side world.');");
    
  }

  void HtmlInputImage1_ServerClick(Object sender, ImageClickEventArgs e)
  {
    
    // Set the inner HTML of the DIV element.
    Div1.InnerHtml = "Hello server-side world.";
    
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom HtmlInputImage - Method - C# Example</title>
    </head>
    <body>
        <form id="form1" runat="server">

            <h3>Custom HtmlInputImage - Method - C# Example</h3>
        
          <aspSample:CustomHtmlInputImageOnPreRender 
            id="HtmlInputImage1" 
        alt="image1.jpg"
            name="HtmlInputImage1"
            runat="server" 
            type="image" 
        src="image1.jpg"
        onserverclick="HtmlInputImage1_ServerClick" />
     
      <br />
      <br />

      <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">
<script runat="server">
  
  Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    
    ' Define the onclick attribute of the custom HtmlInputImage control.
    HtmlInputImage1.Attributes.Add("onclick", "alert('Hello client-side world.');")
    
  End Sub

  Sub HtmlInputImage1_ServerClick(ByVal sender As Object, ByVal e As ImageClickEventArgs)
    
    ' Set the inner HTML of the DIV element.
    Div1.InnerHtml = "Hello server-side world."
    
  End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom HtmlInputImage - Method - Visual Basic Example</title>
    </head>
    <body>
        <form id="form1" runat="server">

            <h3>Custom HtmlInputImage - Method - Visual Basic Example</h3>
        
          <aspSample:CustomHtmlInputImageOnPreRender 
            id="HtmlInputImage1"
                    alt="image1" 
            name="HtmlInputImage1"
            runat="server" 
            type="image" 
                    src="Image1.jpg"
                    onserverclick="HtmlInputImage1_ServerClick" />
      
      <br />
      <br />

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

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

namespace Samples.AspNet.CS.Controls
{
    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public sealed class CustomHtmlInputImageOnPreRender : System.Web.UI.HtmlControls.HtmlInputImage
    {
        protected override void OnPreRender(System.EventArgs e)
        {
            // Call the base class's OnPreRender method.
            base.OnPreRender(e);
            
            // Always display the HtmlInputImage control with no border.
            this.Border = 0;
        }
    }
}

Imports System.Web
Imports System.Security.Permissions

Namespace Samples.AspNet.VB.Controls
    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public NotInheritable Class CustomHtmlInputImageOnPreRender
        Inherits System.Web.UI.HtmlControls.HtmlInputImage

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

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

            ' Always display the HtmlInputImage control with no border.
            Me.Border = 0
        End Sub
    End Class
End Namespace

注解

在 OnPreRender 呈现 HtmlInputImage 控件之前调用 方法。 方法 OnPreRender 主要由扩展控件功能的 HtmlInputImage 控件开发人员使用。

继承者说明

在派生类中重写 OnPreRender(EventArgs) 方法时，请务必调用基类的 OnPreRender(EventArgs) 方法，以便注册的委托接收 PreRender 事件。

适用于

另请参阅