EF 使用遇到过的错误记录备忘

1. is only supported for sorted input in LINQ to Entities  The method ：只支持排序输入实体LINQ 的方法

是使用skip()时没有排序时报的错误

2. Validation failed for one or more entities. 'See EntityValidationErrors' property for more details ：验证失败的一个或多个实体。更多细节见“entityvalidationerrors”属性

修改数据字段的时候报的错误

2.1 关闭ef的实体检查

db.Configuration.ValidateOnSaveEnabled = false

2.2 查看entityvalidationerrors具体那个些字段没有通过

3. 当从数据库取出数据的时候对表中的数据项做扩张方法的时候，例如.ToString()报错。

错误代码：

　　　　　　　　　 var data = from d in Db.Members
                           where d.ID == User_Id
                           select new
                           {
                               d.ID,
                               d.Status
                           };
                var result = from r in data
                             select new
                             {
                                 status = r.Status.Display()
                             };

修改后：

               var data = from d in Db.Members
                           where d.ID == User_Id
                           select new
                           {
                               d.ID,
                               d.Status
                           };
                var result = from r in data.ToList()
                             select new
                             {
                                 status = r.Status.Display()
                             };        

刚取出数据的时候IQueryable<>的类型，把它转换成List();ToList()

4. An entity object cannot be referenced by multiple instances of IEntityChangeTracker：IEntityChangeTracker

单独使用DbContext对象操作

　　　　　　  using (var db = new Context.Create())
            {
                //把使用过的DbContext对象都释放掉
            }

5. entity framework在使用一对一的关系，添加数据不报错，但是数据添加不进去

　　错误的代码：

/**
             * shop:是主表
             * shopCertificate:是shop的从关系(外键)
             * 直接new出外键不会报错,但也添加不了数据
             * 表红的地方,进行外键绑定
             * **/
            using (var db = Context.Default)
            {
                var shop = new Shop()
                {
                    Address = "qwe",
                    Banance = "asd",
                    Certificate = null,
                    City = "zxcf",
                    Description = "rty",
                    District = "fgh",
                    Logo = "vbn",
                    Memo = "uio",
                    Name = "jkl",
                    Provence = "nm",
                    Tax = 0.1m,
                    Status = ShopStatus.Abnormal,
                    Type = null
                };
                var shopCertificate = new ShopCertificate()
                {
                    BankAccountName = "",
                    BankAccountNumber = "",
                    BankName = "",
                    BankNumber = "",
                    CompanName = "",
                    LegalPerson = "",
                    LegalPersonIDCardNumber = "",
                    LegalPersonIDCardPath = "",
                    LicenseNumber = "",
                    LicensePath = "",
                    Status = CompanyStatus.Abnormal,
                    Shop_Id = shop.ID,
                    TaxCertificateNumber = "",
                    TaxCertificatePath = "",
                };
                db.ShopCertificates.Add(shopCertificate);
                db.Shops.Add(shop);
                db.SaveChanges();
            }

　　正确的做法

            using (var db = Context.Default)
            {
                var shop = new Shop()
                {
                    Address = "qwe",
                    Banance = "asd",
                    Certificate = null,
                    City = "zxcf",
                    Description = "rty",
                    District = "fgh",
                    Logo = "vbn",
                    Memo = "uio",
                    Name = "jkl",
                    Provence = "nm",
                    Tax = 0.1m,
                    Status = ShopStatus.Abnormal,
                    Type = null
                };
                //直接用shop的外键关系上再创建新的对象
                //调试可以看到result值为2
                shop.Certificate = new ShopCertificate()
                {
                    BankAccountName = "",
                    BankAccountNumber = "",
                    BankName = "",
                    BankNumber = "",
                    CompanName = "",
                    LegalPerson = "",
                    LegalPersonIDCardNumber = "",
                    LegalPersonIDCardPath = "",
                    LicenseNumber = "",
                    LicensePath = "",
                    Status = CompanyStatus.Abnormal,
                    Shop_Id = shop.ID,
                    TaxCertificateNumber = "",
                    TaxCertificatePath = "",
                };
                db.Shops.Add(shop);
                int result = db.SaveChanges();
            }