/// <summary>
 /// 是否存在
 /// </summary>
 /// <typeparam name="T">类型</typeparam>
 /// <param name="where">查询表达式</param>
 /// <returns></returns>
 public static bool Exists <T>(Expression <Func <T, bool> > where) where T : IEntity
 {
     IsTypeCanBeUsed(typeof(T));
     return(EntityOperationExtensions.DBExists <T>(where));
 }
 /// <summary>
 /// 是否存在
 /// </summary>
 /// <typeparam name="T">类型</typeparam>
 /// <param name="id">id</param>
 /// <returns></returns>
 public static bool Exists <T>(string id) where T : IEntity
 {
     IsTypeCanBeUsed(typeof(T));
     return(EntityOperationExtensions.DBExists <T>(id));
 }