c#中UploadedFile的命名空间是什么?

我得到的类型或命名空间名称在UploadedFile找不到错误。请告诉我UploadedFile的命名空间是什么

 if (RadAsyncUploadAttachmnt.UploadedFiles.Count > 0)
            {
                foreach (UploadedFile file in RadAsyncUploadAttachmnt.UploadedFiles)
                {
                    try
                    {
                        System.Net.Mail.Attachment attachment;
                        string strFileName = string.Empty;
                        strFileName = System.IO.Path.GetFullPath(file.FileName);
                        attachment = new System.Net.Mail.Attachment(file.InputStream, file.GetName());
                        message.Attachments.Add(attachment);
                    }
                    catch { }
                }
            }

谢谢。