ทำคำสั่ง Where ด้วย Combobox ใน Reportviewer แต่ Error ช่วยด้วยคับ C# WinApp

private void button1_Click(object sender, EventArgs e)
        {
            Item tempitem = (Item)lb1.SelectedItem;
            //string cid = tempitem.Value.ToString();
            bill drd = new bill();
            string cs = @"Data Source=MNIKE\SQLEXPRESS;Initial Catalog=Databasefor21;Persist Security Info=True;User ID=sa;Password=1234";
            SqlConnection cn = new SqlConnection(cs);
            SqlDataAdapter da = new SqlDataAdapter("SELECT a.BillID,c.ProductName,b.SealNumber,c.Quantity,c.Fee,d.CustomerName FROM (([Bills] a Join [Billss] b On a.BillID=b.BillID) Join [Products] c On b.SealNumber=c.SealNumber) Join [Customers] d On a.CustomerID=d.CustomerID Where a.CustomerID=@customerid", cn);
            cmd.Parameters.AddWithValue("@customerid",tempitem.Value.ToString());
            da.Fill(drd, drd.Tables[0].TableName);

            ReportDataSource rds = new ReportDataSource("Bills", drd.Tables[0]);
            this.reportViewer1.LocalReport.DataSources.Clear();
            this.reportViewer1.LocalReport.DataSources.Add(rds);
            this.reportViewer1.LocalReport.Refresh();

            this.reportViewer1.RefreshReport();
        }

private void combonamecus()
        {
            SqlConnection con = new SqlConnection(@"Data Source=MNIKE\SQLEXPRESS;Initial Catalog=Databasefor21;Persist Security Info=True;User ID=sa;Password=1234");
            con.Open();
            cmd = new SqlCommand("Select * From Customers");
            cmd.Connection = con;
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                lb1.Items.Add(new Item(reader["CustomerName"].ToString(), Int32.Parse(reader["CustomerID"].ToString())));
            }
            reader.Close();
        }