update a database from dataset - asp.net

Question

as you see in this code i was update the dataset ds at Button1_Click and i want to update the changes made on that dataset to the database.
if i wrote it at the Button1_Click it is work but when i put exactly the same code at Unnamed1_Click it is not working and i dont know why!
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.Configuration;
using System.Data;
using System.Data.SqlClient;
public partial class Discount : System.Web.UI.Page
{
DataSet ds = new DataSet();
public void Page_Load(object sender, EventArgs e)
{
using (SqlConnection con = new SqlConnection("Data Source=Media.ruppin.ac.il;Initial Catalog=igroup9_test1; User ID=igroup9;Password=igroup9"))
{
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Items", con); // יצירת dataAdapter
da.Fill(ds);
GridView2.DataSource = ds;
GridView2.DataBind();
}
}
protected void Button1_Click(object sender, EventArgs e)
{
int price;
for (int i = 0; i < GridView2.Rows.Count; i++)
{
if (Convert.ToInt32(ds.Tables[0].Rows[i].ItemArray[4]) > Convert.ToInt32(minamount.Text))
{
price = Convert.ToInt32(ds.Tables[0].Rows[i][2]);
price -= price * int.Parse(discountrate.Text) / 100;
ds.Tables[0].Rows[i][2] = Convert.ToString(price);
}
}
GridView2.DataSource = ds.Tables[0];
GridView2.DataBind();
//SqlConnection con = new SqlConnection("Data Source=Media.ruppin.ac.il;Initial Catalog=igroup9_test1; User ID=igroup9;Password=igroup9_");
//con.Open();
//SqlDataAdapter tmpda = new SqlDataAdapter("SELECT * FROM Items", con);
//SqlCommandBuilder builder = new SqlCommandBuilder(tmpda);
//tmpda.Update(ds);
}
protected void Unnamed1_Click(object sender, EventArgs e)
{
using (SqlConnection con = new SqlConnection("Data Source=Media.ruppin.ac.il;Initial Catalog=igroup9_test1; User ID=igroup9;Password=igroup9_86098"))
{
con.Open();
SqlDataAdapter tmpda = new SqlDataAdapter("SELECT * FROM Items", con);
SqlCommandBuilder builder = new SqlCommandBuilder(tmpda);
tmpda.Update(ds);
}
}
}

Answer 1

You need to specify the update command for your SqlDataAdapter. Just insert the following code after your commandBuilder instace:
tmpda.UpdateCommand = builder.GetUpdateCommand();