/// <summary>
 /// 获取上传文件随机文件名,返回绝对路径地址
 /// </summary>
 /// <param name="extName">扩展名【请包含 . 】</param>
 /// <param name="virtualPathName">虚路径名(包括文件名称)【/upload/..../filename.ext】</param>
 /// <param name="fileName">文件名带扩展名</param>
 /// <returns></returns>
 public static string GetUploadRandFileName(string extName, out string virtualPathName, out string fileName)
 {
     return(UploadFile.GetUploadRandFileName(GetVirtualDir(), extName, out virtualPathName, out fileName));
 }