HtmlImage.RenderAttributes(HtmlTextWriter) 方法
定义
重要
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将 HtmlImage 控件的属性呈现到指定的 HtmlTextWriter 对象。
protected:
override void RenderAttributes(System::Web::UI::HtmlTextWriter ^ writer);protected override void RenderAttributes (System.Web.UI.HtmlTextWriter writer);override this.RenderAttributes : System.Web.UI.HtmlTextWriter -> unitProtected Overrides Sub RenderAttributes (writer As HtmlTextWriter)参数
- writer
- HtmlTextWriter
包含要在客户端上呈现的输出流的 HtmlTextWriter。
例外
Src 属性包含格式不正确的 URL。
示例
下面的代码示例演示如何重写 RenderAttributes 自定义服务器控件中的方法，以便始终随控件一起 HtmlImage 显示特定可选文本（作为工具提示进行访问）。
<%@ 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 HtmlImage - RenderAttributes - C# Example</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom HtmlImage - RenderAttributes - C# Example</h3>
<aspSample:CustomHtmlImageRenderAttributes id="Img1"
runat="server"
border="0"
src="image.jpg" />
</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 HtmlImage - RenderAttributes - Visual Basic Example</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom HtmlImage - RenderAttributes - Visual Basic Example</h3>
<aspSample:CustomHtmlImageRenderAttributes id="Img1"
runat="server"
border="0"
src="image.jpg" />
</form>
</body>
</html>
using System.Web;
using System.Security.Permissions;
namespace Samples.AspNet.CS.Controls
{
[AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
public sealed class CustomHtmlImageRenderAttributes : System.Web.UI.HtmlControls.HtmlImage
{
protected override void RenderAttributes(System.Web.UI.HtmlTextWriter writer)
{
// Call the base class's RenderAttributes method.
base.RenderAttributes(writer);
// Write out the HtmlImage control's alt tag.
writer.Write(" alt=\"Text from custom RenderAttributes method.\"");
}
}
}
Imports System.Web
Imports System.Security.Permissions
Namespace Samples.AspNet.VB.Controls
<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomHtmlImageRenderAttributes
Inherits System.Web.UI.HtmlControls.HtmlImage
Protected Overrides Sub RenderAttributes(ByVal writer As System.Web.UI.HtmlTextWriter)
' Call the base class's RenderAttributes method.
MyBase.RenderAttributes(writer)
' Write out the HtmlImage control's alt tag.
writer.Write(" alt=""Text from custom RenderAttributes method.""")
End Sub
End Class
End Namespace
注解
如果属性的值 Src 是格式不正确的 URL，该方法 RenderAttributes 将引发异常 HttpException 。
该方法 RenderAttributes 重写基类 RenderAttributes 的方法以写入 src 呈现 HtmlImage 控件的属性。
该方法 RenderAttributes 主要由扩展控件功能的 HtmlImage 控件开发人员使用。