根据LINQ to SQL中插入记录的ID更新记录

Question

我想插入一条记录，然后根据插入记录的scope_identity更新记录。 我这样做但是当我想更新我的记录时遇到错误。

WorkshopDataContext Dac = new WorkshopDataContext();
Dac.Connection.ConnectionString = "Data Source=dpsxxx-xxx;Initial Catalog=kar;User ID=sa;Password=xxxx";
Tbl_workshop Workshop = new Tbl_workshop();
Workshop.StateCode = Bodu.BduStateCode;
Workshop.CityCode = Bodu.BduCityCode;
Workshop.Co_workshop=12222;
Dac.Tbl_workshop.InsertOnSubmit(Workshop);
Dac.SubmitChanges();
Int64 Scope = Workshop.id;
var query = from record in Dac.Tbl_workshop where record.id == Scope select record;
        query.First().co_Workshop = Scope;
Dac.SubmitChanges();

这是错误：

Value of member 'co_Workshop' of an object of type 'Tbl_Workshop' changed.
A member defining the identity of the object cannot be changed.
Consider adding a new object with new identity and deleting the existing one instead.

Answer 1

正如它在错误上所说，你不能改变co_Workshop因为它的身份（自动增量值）。要自由编辑它，您需要编辑数据库并删除此设置。

可能发生的是id和co_Workshop都设置为identity。只需禁用co_Workshop的身份复选框。

Answer 2

如果您已正确配置Linq-to-SQL模型以反映表格中的IDENTITY列，则应在.SubmitChanges()之后立即获得新值：

Tbl_workshop Workshop = new Tbl_workshop();
Workshop.StateCode = Bodu.BduStateCode;
Workshop.CityCode = Bodu.BduCityCode;
Workshop.Co_workshop=12222;

Dac.Tbl_workshop.InsertOnSubmit(Workshop);
Dac.SubmitChanges();

Int64 workshopID = Workshop.Id;  // you should get new ID value here - automatically!!

您无需执行任何操作，例如从SQL Server或其他任何内容中读取新值 - Linq-to-SQL应使用正确的值自动更新Workshop对象。

更新：将co_workshop值更新为IDENTITY ID给出的值，执行此操作（只需设置co_workshop的值并再次保存 - 那就是真的所有）：

Dac.Tbl_workshop.InsertOnSubmit(Workshop);
Dac.SubmitChanges();

Int64 workshopID = Workshop.Id;  // you should get new ID value here - automatically!!

Workshop.Co_workshop = workshopID;
Dac.SubmitChanges();