EntityType 'UserInfo' has no key defined. Define the key for this EntityType.

One or more validation errors were detected during model generation:

 System.Data.Edm.EdmEntityType: : EntityType 'UserInfo' has no key defined. Define the key for this EntityType.  System.Data.Edm.EdmEntitySet: EntityType: EntitySet �UserInfo� is based on type �UserInfo� that has no keys defined.

遇见这个问题，我觉得很奇特，因为事实上我已经为'UserInfo'这个类定义了[KEY]的类注释。

然后又提示我找不到Key。见下面的代码

    public class UserInfo
    {
        [Key]
        public int UserID;
        public string UserName;
        public string Password;
        public int UseState;
        public string Email;
        public DateTime AddTime;
        public int AddUser_ID;
        public string ImgUrl;
        public virtual UserType UserTypes { get; set; }
    }

后面在stackoverflow上找到了答案。EF会自动识别一个实体的主键只要主键的名称符号 'Id'或 '实体名Id'. 另外，它必须声明成属性，访问权限必须是Public的。这个错误是因为我将UserId声明成了一个字段，只要修改成属性就OK了。修改后的代码如下所示。

    public class UserInfo
    {
        [Key]
        public int UserID { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }
        public int UseState { get; set; }
        public string Email { get; set; }
        public DateTime AddTime { get; set; }
        public int AddUser_ID { get; set; }
        public string ImgUrl{ get; set; }
        public virtual UserType UserTypes { get; set; }
    }

2013-01-10  16:50:05