.net4.0 调用API（form-data）上传文件及传参/// <summary> /// /// </summary> /// <param name="url">API URL</param> /// <param name="token">API token</param> /// <param name="parameters">API参数(除文件类型外)</param> /// <param name="fileContent">文件参数(二进制文件流)</param> /// <param name="fileName">文件名</param> /