Cannot insert data in .sdf database in Windows Forms Application

[dineshA]

I am unable to insert data into database, plz help me out.
This is my code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace labsoft
{
    public partial class test_group : Form
    {
        Form opener;

        public test_group(Form parentForm)
        {
            InitializeComponent();
            opener = parentForm;
        }

        System.Data.SqlServerCe.SqlCeConnection con;
        System.Data.SqlServerCe.SqlCeDataAdapter da;
        DataSet ds1;


        int MaxRows = 0;
        int inc = 0;

        private void Form2_Load(object sender, EventArgs e)
        {
            // TODO: This line of code loads data into the 'labworkDataSet1.test_main_group' table. You can move, or remove it, as needed.
            this.test_main_groupTableAdapter.Fill(this.labworkDataSet1.test_main_group);
            con = new System.Data.SqlServerCe.SqlCeConnection();
            con.ConnectionString = "Data Source=C:\\Users\\Dinesh\\Documents\\Visual Studio 2008\\Projects\\labsoft\\labsoft\\labwork.sdf";
            con.Open();
            ds1 = new DataSet();

            da = new System.Data.SqlServerCe.SqlCeDataAdapter();

            con.Close();
        }

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {

           DataRow dRow =  ds1.Tables["test_main_group"].NewRow();
            dRow[1] = richTextBox1.Text;

            ds1.Tables["test_main_group"].Rows.Add(dRow);
            System.Data.SqlServerCe.SqlCeCommandBuilder cb;
            cb = new System.Data.SqlServerCe.SqlCeCommandBuilder(da);
            cb.DataAdapter.Update(ds1.Tables["test_main_group"]);

            MaxRows = MaxRows + 1;
            inc = MaxRows - 1;

            MessageBox.Show("added successfully");
        }

    }
}

Thank You in Advance for any answer

[Benjamin_6]

You generally need to leave some kind of error or at least more detail if you want to get help here.

[dineshA]

This is the warning i am getting.