HtmlInputImage.RenderAttributes Method
Assembly: System.Web (in system.web.dll)
protected void RenderAttributes ( HtmlTextWriter writer )
protected override function RenderAttributes ( writer : HtmlTextWriter )
Not applicable.
Parameters
- writer
The HtmlTextWriter that contains the output stream to render on the client.
| Exception type | Condition |
|---|---|
| The Src property contains a malformed URL. |
The RenderAttributes method resolves the URL set in the Src property, writes the onclick attribute of the rendered HtmlInputImage control if the CausesValidation property is true, and finally calls the base RenderAttributes method. If the value of the Src property is a malformed URL, an HttpException exception is thrown.
The RenderAttributes method is used primarily by control developers extending the functionality of the HtmlInputImage control.
The following code example demonstrates how to override the RenderAttributes method in a custom server control so that specific alternate text, accessible as a ToolTip, is always displayed with the HtmlInputImage.
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.JSL.Controls" Assembly="Samples.AspNet.JSL" %>
<%@ Page Language="VJ#" 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 HtmlInputImage - RenderAttributes - VJ# Example</title>
<script runat="server">
void Page_Load(Object sender, EventArgs e)
{
HtmlInputImage1.get_Attributes().Add("onclick",
"alert('Hello client-side world.');");
} //Page_Load
void HtmlInputImage1_ServerClick(Object sender, ImageClickEventArgs e)
{
Div1.set_InnerHtml("Hello server-side world.");
} //HtmlInputImage1_ServerClick
</script>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom HtmlInputImage - RenderAttributes - VJ# Example</h3>
<aspSample:CustomHtmlInputImageRenderAttributes
id="HtmlInputImage1"
name="HtmlInputImage1"
runat="server"
type="image"
src="http://www.microsoft.com/homepage/gif/bnr-microsoft.gif"
alt="Microsoft"
onserverclick="HtmlInputImage1_ServerClick" /><br />
<br />
<div
id="Div1"
runat="server"
style="DISPLAY: inline; WIDTH: 256px; HEIGHT: 15px" />
</form>
</body>
</html>
package Samples.AspNet.JSL.Controls;
public class CustomHtmlInputImageRenderAttributes
extends System.Web.UI.HtmlControls.HtmlInputImage
{
protected void RenderAttributes(System.Web.UI.HtmlTextWriter writer)
{
// Add an ALT attribute to the the HtmlInputImage control.
writer.Write(" alt='Microsoft'");
// Call the base's RenderAttributes method.
super.RenderAttributes(writer);
} //RenderAttributes
} //CustomHtmlInputImageRenderAttributes