Mine

ALTER PROCEDURE [dbo].[sp2_GetAllCategories] 
	@SortDirection varchar (5) = NULL,
	@SortExpression varchar(50) = NULL
AS
BEGIN
	SET NOCOUNT ON;

	DECLARE @sql varchar(Max)
	SET @sql = 'SELECT * FROM Categories ORDER BY ' + ISNULL(@SortExpression, 'CategoryNameEN') + ' ' +  ISNULL(@SortDirection, 'ASC')  
	EXEC (@sql)    

END