Refresh GridView after data gets updated using C# in ASP.Net

I have a gridview. When I edit records, records only update in the database, not in client side. In client side, old records are displayed.

I want to refresh gridview when I click update button so that records in database will be displayed in client side.

This is the code:

    protected void Update(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        foreach (GridViewRow row in grid1.Rows)
        {
            int id = int.Parse((row.FindControl("LblOrderId") as Label).Text);
            int orderAmount = int.Parse((row.FindControl("txtOrderAmount") as TextBox).Text);
            int affec = UpdateAmount(orderAmount, id);            
        }        
    }

    public int UpdateAmount(int amount, int id)
    {
        using (SqlConnection con = Connection_Manager.connection_String())
        {
            con.Open();
            string sql = "update order_test set amount = @amount where id=@id";
            SqlCommand cmd = new SqlCommand(sql, con);
            cmd.Parameters.AddWithValue("@amount", amount);
            cmd.Parameters.AddWithValue("@id", id);
            int affected = cmd.ExecuteNonQuery();
            return affected;
        }
    }