Stored Procedure Problem Using Un Quoted Varchar

I have a stored procedure which returns a count of products and a limited number of rows from a query.

I am using SQL Server 2005 and calling the procedure in asp.net

The procedure is as follows





Code Snippet

GO
ALTER PROCEDURE [dbo].[GetProductsByCategoryId]
@Category VARCHAR(255),
@Range INT,
@PageIndex INT,
@NumRows INT,
@CategoryName nvarchar(255) OUTPUT,
@CategoryProductCount INT OUTPUT
AS

BEGIN

/*
Get product count
*/
SELECT @CategoryProductCount=(SELECT COUNT(*) FROM Products LEFT JOIN tblVar on Products.ProductID = tblVar.prodidvar WHERE Products.Category=@Category AND Products.Range=@Range)

/*set row variables*/
Declare @startRowIndex INT;
set @startRowIndex =(@PageIndex * @NumRows) + 1;

/* get full list of products */
With ProductEntries as (
SELECT ROW_NUMBER() OVER (ORDER BY Products.ProductID, tblVar.idvar ASC) as Row, field1, field2
FROM Products LEFT JOIN tblVar on Products.ProductID=tblVar.prodidvar
WHERE Range=@Range
AND Category = @Category
)



/*get only needed rows */
SELECT field1, field2
FROM ProductEntries
WHERE Row Between
@startRowIndex and @startRowIndex+@NumRows-1


END

The problem seems to be with the line

AND Category = @ Category
in the query to make the ProductEntries

If I take this query and run it in an SQL pane I need to enclose the argument for @Category in single quotes.
If I try to do this in the procedure it simply searchs for @Category as a string rather than the value of @Category.

The query returns and displays results with no problems without this line, and also if it is returning a result set that has no values in tblVar to join to.

Also if I run the query on just the Products table removing the left join it will return results with no problems.


Thanks to anyone who can help!

And I apologise if it is something simple but asp and SQL Server is not my usual coding platform.