I think, it's not a one time thing. You need to set it ON before insertion and then reset it back to OFF for keeping consistency.
You can try the following. Executes these queries in your submitchanges() method:
SET IDENTITY_INSERT tblOrderItemStatus ON
Insert Into tblTest(Test_Id,Test_Name) values(4, "TestTemp4″)
SET IDENTITY_INSERT tblOrderItemStatus OFF