.Net发出图片Request请求

Stream reader = null;

                //可能是外部链接

                if (imgUrl.ToLower().StartsWith("http://"))

                {

                    var request = System.Net.WebRequest.Create(imgUrl);

                    var response = request.GetResponse();

                    reader = response.GetResponseStream();

                }

                else

                {

                    reader = new FileStream( System.Web.HttpContext.Current.Server.MapPath( imgUrl ), FileMode.Open );

                }