How to get the next auto-increment id in linq

In addition to solution 1 by OriginalGriff[^], i'd suggest to read these:
c# - Autonumber with Entity Framework - Stack Overflow[^]
c# - Can I return the 'id' field after a LINQ insert? - Stack Overflow[^]
linq to sql - How to increment primary key without using Auto Increment in MySql - Stack Overflow[^]

/* Begin Stored Procedure */
USE [MyDatabase]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE [dbo].[My_StoredProcedure]
@VariableNum [int] = NULL,
@VariableDate [datetime] = NULL,
...
...
@Variable_Return_Id [int] OUTPUT
WITH EXECUTE AS CALLER
AS
Begin
INSERT INTO
My_Table(Var_Num ,
Var_Date ,
... ,
...

) VALUES (@VariableNum ,
@VariableDate
....
....
)
SET @Variable_Return_Id = @@IDENTITY
End
/* End Stored Procedure */

Note : You must create this stored procedure in SQL Server data table and add Visual studio project Linq dbml in My_StoredProcedure with drop down.
When you call is My_StoredProcedure add a new record and Return IDENTITY Number.

C# Example:
int AddRec()
{
int num=1;
DateTime DateVal = DateTime.Now.Date;
int ResultId;
ResultId=My_StoredProcedure(num, DateVal);
return(ResultId);
}

VB Example:
Function AddRec() as integer
Dim num As Integer = 1
Dim DateVal As DateTime = DateTime.Now.Date
Dim ResultId As integer
ResultId=My_StoredProcedure(num, DateVal)
AddRec=ResultId ' or Return ResultId
End Function

If using LINQ, then to get new value assigned to the Identity column is very simple. You don't need these many Stored Procedures to be invoked. You already have the object instance to be added, then simply read the Id property of this object after DB. SaveChanges() is invoked.