using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.Sql;
using System.Data.SqlClient;
namespace WebApplication9
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            getcategory();
        }
        void getcategory()
        {
            SqlConnection conn = new SqlConnection();
            conn.ConnectionString = "Data Source=HOME\\SQLEXPRESS;Initial Catalog=AdventureWorks;Integrated Security=True";
            SqlCommand cmd = new SqlCommand();
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = "sp_products3";
            cmd.Connection = conn;
            try
            {
                conn.Open();
                SqlDataReader datareader = cmd.ExecuteReader();
                while (datareader.Read())
                {
                    ListBox1.Items.Add(datareader.ToString());
                }
                datareader.Close();
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message);
            }
            finally
            {
                conn.Close();
            }
        }
        void getproductcategory()
        {
            SqlConnection conn = new SqlConnection();
            conn.ConnectionString = "Data Source=HOME\\SQLEXPRESS;Initial Catalog=AdventureWorks;Integrated Security=True";
            SqlCommand cmd = new SqlCommand();
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = "sp_productid1";
            cmd.Connection = conn;
            SqlParameter param = new SqlParameter();
            param.ParameterName = "@ProductSubcategoryID";
             Convert.ToInt64(הבעיה היא כאן!);   
            
            try
            {
                conn.Open();
                SqlDataReader datareader = cmd.ExecuteReader();
                while (datareader.Read())
                {
                    ListBox2.Items.Add(datareader.ToString());
                }
                datareader.Close();
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message);
            }
            finally
            {
                conn.Close();
            }
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            ListBox1.Visible = false;
            Button1.Visible = false;
            ListBox2.Visible = true;
            Button2.Visible = true;
            getproductcategory();
        }
        protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
        }
    }
}

create proc sp_productid2
@ProductSubcategoryID bigint
as
begin
select * from . where productid = @ProductSubcategoryID
end
go
exec sp_productid2