ImageButton.OnPreRender(EventArgs) 方法
定义
重要
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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 -> unitProtected Overrides Sub OnPreRender (e As EventArgs)Protected Friend Overrides Sub OnPreRender (e As EventArgs)参数
示例
下面的代码示例演示如何重写 OnPreRender 方法，以便始终在自定义 ImageButton 服务器控件中显示精简边框。
备注
下面的代码示例使用单文件代码模型，如果直接复制到代码隐藏文件中，可能无法正常工作。 代码示例的第一部分必须复制到具有 .aspx 扩展名的空文本文件中。 第二部分必须位于 C#) 的 .cs 文件 (中，或者Visual Basic) 的 .vb 文件 (。 有关Web Forms代码模型的详细信息，请参阅 ASP.NET Web Forms页代码模型。
<%@ 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 ImageButton - OnPreRender - C# Example</title>
<script runat="server">
void ImageButton1_Command(Object sender, CommandEventArgs e)
{
// Redirect to the Microsoft home page.
Response.Redirect("http://www.microsoft.com/");
}
</script>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom ImageButton - OnPreRender - C# Example</h3>
<aspSample:CustomImageButtonOnPreRender
id="ImageButton1"
runat="server"
OnCommand="ImageButton1_Command"
AlternateText="Microsoft Home"
ImageUrl="http://www.microsoft.com/homepage/gif/bnr-microsoft.gif" />
</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 ImageButton - OnPreRender - VB.NET Example</title>
<script runat="server">
Sub ImageButton1_Command(sender As Object, e As CommandEventArgs)
' Redirect to the Microsoft home page.
Response.Redirect("http://www.microsoft.com/")
End Sub
</script>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom ImageButton - OnPreRender - VB.NET Example</h3>
<aspSample:CustomImageButtonOnPreRender id="ImageButton1" runat="server"
OnCommand="ImageButton1_Command" AlternateText="Microsoft Home"
ImageUrl="http://www.microsoft.com/homepage/gif/bnr-microsoft.gif" />
</form>
</body>
</html>
using System;
using System.Web;
using System.Web.UI.WebControls;
using System.Security.Permissions;
namespace Samples.AspNet.CS.Controls
{
[AspNetHostingPermission(SecurityAction.Demand,
Level = AspNetHostingPermissionLevel.Minimal)]
public class CustomImageButtonOnPreRender : ImageButton
{
protected override void OnPreRender(EventArgs e)
{
// Run the OnPreRender method on the base class.
base.OnPreRender(e);
// Always display the ImageButton with a thin border.
this.BorderWidth = Unit.Point(1);
}
}
}
<AspNetHostingPermission(SecurityAction.Demand, _
Level:=AspNetHostingPermissionLevel.Minimal)> _
Public Class CustomImageButtonOnPreRender
Inherits ImageButton
Protected Overrides Sub OnPreRender(ByVal e As EventArgs)
' Run the OnPreRender method on the base class.
MyBase.OnPreRender(e)
' Always display the ImageButton with a thin border.
Me.BorderWidth = Unit.Point(1)
End Sub
End Class
注解
从控件派生自定义类ImageButton时，该方法OnPreRender主要由控件开发人员使用。