/// <summary>
 /// 初始化
 /// </summary>
 private void Init()
 {
     if (Setting == null)
     {
         Setting = OssConfig.OssSetting;
     }
     if (Setting == null)
     {
         throw new  Exception("请先配置OssSetting!");
     }
 }
 /// <summary>
 /// 构造函数
 /// </summary>
 /// <param name="ossSetting">设置文件</param>
 public Context(OssSetting ossSetting)
 {
     Setting = ossSetting;
     Init();
 }