passing arguments problem in store procedure

USE [BrandMutual]
GO
/****** Object:  StoredProcedure [dbo].[SP_Product_Get]    Script Date: 03/02/2013 14:46:50 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[SP_Product_Get]
(
			 @id int=0,
                   @Action nvarchar(MAX)='',
                  @category nvarchar(50)=''
		
)
As
SET NOCOUNT ON
if(@id=0)
Begin
         Select * From tbl_admin_product_add
		
                     
End


if(@id>0 AND  @Action='S1' )

Begin
 Select * From tbl_admin_product_add
 where 
  id= @id
  
  E
if(@id>0 AND  @Action='S2' )
Begin
 Select * From tbl_admin_product_add
 where 
  category = @category 
  
  End


SET NOCOUNT OFF

public IEnumerable<tbl_admin_product_add> GetProductDetails()
   {
 int id=0;

       var v = li.SP_Product_Get(id);

       return (from c in v
               select new tbl_admin_product_add()
               {
                   id = c.id,
                   category = c.category,

               }
              ).ToList();


   }