HtmlImage.RenderAttributes Method (HtmlTextWriter)

 

Renders the HtmlImage control's attributes to the specified HtmlTextWriter object.

Namespace:   System.Web.UI.HtmlControls
Assembly:  System.Web (in System.Web.dll)

protected override void RenderAttributes(
	HtmlTextWriter writer
)

Parameters

writer
Type: System.Web.UI.HtmlTextWriter

The HtmlTextWriter that contains the output stream to render on the client.

Exception Condition
HttpException

The Src property contains a malformed URL.

If the value of the Src property is a malformed URL, the RenderAttributes method throws an HttpException exception.

The RenderAttributes method overrides the base class's RenderAttributes method to write the src attribute of the rendered HtmlImage control.

The RenderAttributes method is used primarily by control developers extending the functionality of the HtmlImage control.

The following code example demonstrates how to override the RenderAttributes method in a custom server control so that specific alternative text, accessible as a ToolTip, is always displayed with the HtmlImage 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 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>
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.\"");
        }
    }
}

.NET Framework
Available since 1.1
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