HtmlInputCheckBox.OnPreRender(EventArgs) 方法
定义
引发 OnPreRender(EventArgs) 事件并将该控件注册为需要回发处理的控件。Raises the OnPreRender(EventArgs) event and registers the control as one that requires postback handling.
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
示例
下面的代码示例演示如何重写 OnPreRender 自定义服务器控件中的方法,以便将 Title 特性添加到每个 HtmlInputCheckBox 控件中。The following code example demonstrates how to override the OnPreRender method in a custom server control so that a Title attribute is added to each 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
注解
OnPreRender方法将重写基 OnPreRender 方法。The OnPreRender method overrides the base OnPreRender method. OnPreRender 主要由控件开发人员使用。OnPreRender is used primarily by control developers.