Help with Stored Procedure

The following Stored procedure can be called with no parameter where I want it to return ALL records,
or with a single paramater where it should only return those where TC.PostCodeID = @postcode.

The SP works when using a parameter, the problem is that when no paramaters are given only those where TC.PostCodeID Is Not Null are returned.

So the question is I want it to return ALL records including those where TC.PostCodeID = NULL when no paramaters are used.


NOTE: This is only an example, the WHERE clause contains further paramaters. I have also tried setting ANSI_NULLS OFF before creating the SP!


CREATE PROC spTest ( @Postcode int=Null )

AS
SELECT * FROM  tblContact TC
WHERE TC.PostCodeID =  IsNull(@PostCode, TC.PostCodeID)