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When you create a Generic Handler, you create a file that ends with the extension .ashx. Whenever you request the .ashx file, the Generic Handler executes.
A Generic Handler is like an ASP.NET page that contains a single method that renders content to the browser.
You can't add any controls declaratively to a Generic Handler.
A Generic Handler doesn't support events such as the Page Load or Page PreRender events.
File: ImageTextHandler.ashx
<%@ WebHandler Language="C#" Class="ImageTextHandler" %>
using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
public class ImageTextHandler : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
string text = context.Request.QueryString["text"];
string font = context.Request.QueryString["font"];
string size = context.Request.QueryString["size"];
Font fntText = new Font(font, float.Parse(size));
Bitmap bmp = new Bitmap(10, 10);
Graphics g = Graphics.FromImage(bmp);
SizeF bmpSize = g.MeasureString(text, fntText);
int width = (int)Math.Ceiling(bmpSize.Width);
int height = (int)Math.Ceiling(bmpSize.Height);
bmp = new Bitmap(bmp, width, height);
g.Dispose();
g = Graphics.FromImage(bmp);
g.Clear(Color.White);
g.DrawString(text, fntText, Brushes.Black, new PointF(0, 0));
g.Dispose();
bmp.Save(context.Response.OutputStream, ImageFormat.Gif);
}
public bool IsReusable
{
get
{
return true;
}
}
}
You specify the image that you want to return from the handler by making a request that looks like this:
/ImageTextHandler.ashx?text=Hello&font=Arial&size=30
The IsReusable property indicates whether the same handler can be reused over multiple requests.
The following page uses the ImageTextHandler.ashx file.
<%@ Page Language="C#" %>
<!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 id="Head1" runat="server">
<title>Show ImageTextHandler</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<img src="ImageTextHandler.ashx?text=Some Text&font=WebDings&size=42" />
<br />
<img src="ImageTextHandler.ashx?text=Some Text&font=Comic Sans MS&size=42" />
<br />
<img src="ImageTextHandler.ashx?text=Some Text&font=Courier New&size=42" />
</div>
</form>
</body>
</html>
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