protected void insrtbtn_Click(object sender, EventArgs e)
    {
        dataTable.Rows.Add(procode.Text, pnamedrp.SelectedItem.Text, protypee.SelectedItem.Text, proprice.Text, proqunty.Text, amt.Text + "");
        salegrid.DataSource = dataTable;
        salegrid.DataBind();
        setupTable();
        updateTotal();
        con.Open();
        string query5 = "select prostock from

string query5 = "select prostock from inventory where Proname='" + pnamedrp.Text + " ' and prostock=prostock<75";
        {
            Response.Write("<script>alert('Purchase Product')</script>");
        }
            SqlCommand comd = new SqlCommand("insert into sales values(@billno,@Cid,@Proid,@Proname,@protype,@sellingprice,@quantity,@cost)", con);

"Select @@identity;" in