asp.net下结合HttpHandler实现图片防盗链

#region IHttpHandler 成员 
bool IHttpHandler.IsReusable 
{ 
get { return true; } 
} 
void IHttpHandler.ProcessRequest(HttpContext context) 
{ 
string FileName = context.Server.MapPath(context.Request.FilePath); 
if (context.Request.UrlReferrer.Host == null) 
{ 
context.Response.ContentType = "image/JPEG"; 
context.Response.WriteFile("/no.jpg"); 
} 
else 
{ 
if (context.Request.UrlReferrer.Host.IndexOf("mydomain.com") > 0) 
{ 
context.Response.ContentType = "image/JPEG"; 
context.Response.WriteFile(FileName); 
} 
else 
{ 
context.Response.ContentType = "image/JPEG"; 
context.Response.WriteFile("no/jpg"); 
} 
} 
} 
#endregion 
 
<httpHandlers> 
<add verb="*" path="*.jpg" type="JpgHandler, MyDll" /> 
</httpHandlers>