Problem in implementing stored procedure

create proc ap_InventoryByMakeModel_Count
  @Make varchar(50) = null, -- criteria
  @Model varchar(50) = null, -- criteria
    @Count int output

as


select @Count = count(*)
from dbo.InventorySum
where Make like @Make
and Model like @Model

return

namespace WebApplication3
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected int currentPageNumber = 1;
        private const int PAGE_SIZE = 25;
        
         private void BindData()
        {
            int count=0;
            string make = Request.QueryString["param1"];
            string model = Request.QueryString["param2"];
            DataClasses1DataContext asset = new DataClasses1DataContext();
            var query = asset.ap_InventoryByMakeModel_Quick3(make, model, 444, 1);
            GridView1.DataSource = query;
            GridView1.DataBind();
            double totalRows = asset.ap_InventoryByMakeModel_Count(make, model,ref count);


            lblTotalPages.Text = CalculateTotalPages(totalRows).ToString();

            lblCurrentPage.Text = currentPageNumber.ToString();

            if (currentPageNumber == 1)
            {
                Btn_Previous.Enabled = false;

                if (Int32.Parse(lblTotalPages.Text) > 0)
                {
                    Btn_Next.Enabled = true;
                }
                else
                    Btn_Next.Enabled = false;

            }

            else
            {
                Btn_Previous.Enabled = true;

                if (currentPageNumber == Int32.Parse(lblTotalPages.Text))
                    Btn_Next.Enabled = false;
                else Btn_Next.Enabled = true;
            }


        }

         private int CalculateTotalPages(double totalRows)
         {
             int totalPages = (int)Math.Ceiling(totalRows / PAGE_SIZE);

             return totalPages;
         }
         protected void ChangePage(object sender, CommandEventArgs e)
         {

             switch (e.CommandName)
             {
                 case "Previous":
                     currentPageNumber = Int32.Parse(lblCurrentPage.Text) - 1;
                     break;

                 case "Next":
                     currentPageNumber = Int32.Parse(lblCurrentPage.Text) + 1;
                     break;
             }

             BindData();
         }

         protected void Page_Load(object sender, EventArgs e)
         {
             BindData();
         }
    }
   

}