防盗链

            //获取请求来的Referrer
            Uri referrerUrl = context.Request.UrlReferrer;

            //获取请求的URL
            Uri requestUrl = context.Request.Url;

            if(Uri.Compare(referrerUrl,requestUrl,UriComponents.HostAndPort,UriFormat.SafeUnescaped,StringComparison.CurrentCulture)==0)
            {
                context.Response.WriteFile("101.jpg");
            }
            else
            {
                context.Response.WriteFile("11.jpg");
            }