This occurs when you have a (Primary key) column that is not set to Is Identity to true in SQL and you don't pass explicit value thereof during insert. It will take the first row, then you wont be able to insert the second row, the error will pop up. This can be corrected by adding this line of code [DatabaseGenerated(DatabaseGeneratedOption.Identity)] in your PrimaryKey column and make sure its set to a data type int. If the column is the primary key and is set to IsIDentity to true in SQL there is no need for this line of code [DatabaseGenerated(DatabaseGeneratedOption.Identity)] this also occurs when u have a column that is not the primary key, in SQL that is set to Is Identity to true, and in your EF you did not add this line of code [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

如果您使用Oracle SQL Developer进行连接，请记住添加/sqldev:stmt/

/sqldev:stmt/ set identity_insert TABLE on

如果您使用Interface并以通用方式实现savechanges方法，则会出现使用非类型化DBContext或DBSet的问题

如果这是您的情况，我建议使用强类型的dbcontext

MyDBContext.MyEntity.Add(mynewObject)

那么，保存更改就可以了

即使一切正确，如果Identity列的数据类型不是int或long，也会出现此错误。我有单位列为十进制，虽然我只保存int值(我的坏)。更改数据库和底层模型中的数据类型为我解决了这个问题。

在我的例子中，我已经在modelBuilder的上下文中设置了另一个属性作为键。

modelBuilder.Entity<MyTable>().HasKey(t => t.OtherProp);

我必须设置正确的id

 modelBuilder.Entity<MyTable>().HasKey(t => t.Id);

你可以简单地使用这句话，例如，如果你的表名是学校。 在插入之前，确保identity_insert设置为ON，在插入查询之后，将identity_insert设置为OFF

SET IDENTITY_INSERT School ON
/*
  insert query
  enter code here
*/
SET IDENTITY_INSERT School OFF