SQL sets the default value getdate () LINQ to SQL. A new data record is still null.

When the default value getdate () is set, the new data is still null. This problem does not occur when you use the SQL statement insert, but the problem occurs when you use the LINQ to SQL statement.

Solution: http://msdn.microsoft.com/zh-cn/library/system.data.linq.mapping.columnattribute.isdbgenerated.aspx

[Column (storage = "  _ Orderid  " , Autosync = autosync. oninsert, dbtype = "  Int not null identity  " , Isprimarykey = True , Isdbgenerated = True  )]  Public   Int Orderid {  Get  {  Return   This  . _ Orderid ;}  Set  {  If (( This . _ Orderid! = Value )){  This  . Onorderidchanging (value );  This . Sendpropertychanging ();  This . _ Orderid = Value;  This . Sendpropertychanged ( "  Orderid  "  );  This  . Onorderidchanged ();}}} 

Isdbgenerated =True is the key to solving the problem.