SQL problem in saving [SOLVED]

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;
using System.Data.SqlServerCe;

namespace SQL_Editor
{
    public partial class MainForm : Form
    {
        DataSet ds = new DataSet();
        SqlCeConnection cn;
        SqlCeDataAdapter da;
        string DefaultConnectionString;
        string DatabaseFile;
        string TableName;

        public MainForm()
        {
            InitializeComponent();
            DefaultConnectionString = Properties.Settings.Default.DefaultConnectionString;
        }

        private void Load_Click(object sender, EventArgs e)
        {
            //////////
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "sdf files (*.sdf)|*.sdf|mdf files (*.mdf)|*.mdf|All files (*.*)|*.*";
            ofd.RestoreDirectory = true;
            if (ofd.ShowDialog() != DialogResult.OK)
                return;
            DatabaseFile = ofd.FileName;
            //////////
            if (CheckSaveChanges() == DialogResult.Cancel)
                return;
            try
            {
                string ConnectionStr = DefaultConnectionString.Replace("<DatabaseFileName>", DatabaseFile);
                SqlCeConnection cn1 = new SqlCeConnection(ConnectionStr);
                cn1.Open();
                string strSql = "SELECT * FROM INFORMATION_SCHEMA.TABLES";
                SqlCeDataAdapter da1 = new SqlCeDataAdapter(strSql, cn1);
                DataSet ds1 = new DataSet();
                ds1.Clear();
                da1.Fill(ds1);
                cn1.Close();
                TableSelect tbslc = new TableSelect();
                for (int i = 0; i < ds1.Tables[0].Rows.Count; i++)
                    tbslc.Add(ds1.Tables[0].Rows[i][2].ToString());
                tbslc.ShowDialog();
                if (tbslc.TableResult == "")
                    return;
                else
                    TableName = tbslc.TableResult;
                cn = new SqlCeConnection(ConnectionStr);
                cn.Open();
                strSql = "SELECT * FROM " + TableName;
                da = new SqlCeDataAdapter(strSql, cn);
                ds.Clear();
                da.FillSchema(ds, SchemaType.Source);
                da.Fill(ds, TableName);
                //ds.Tables[0].PrimaryKey = new System.Data.DataColumn[] { ds.Tables[0].Columns[0], ds.Tables[0].Columns[1], ds.Tables[0].Columns[2] };
                //////////
                dataGrid1.DataBindings.Clear();
                dataGrid1.DataBindings.Add(new Binding("DataSource", ds, TableName));
                //////////
                cn.Close();
                //Clipboard.GetDataObject().GetData(DataFormats.Text)
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString(), "Error");
            }
        }

        private void Option_Click(object sender, EventArgs e)
        {
            Option opt = new Option();
            opt.textBox_ConnectionString.Text = DefaultConnectionString;
            opt.ShowDialog();
            if (opt.OK_result)
            {
                DefaultConnectionString = opt.textBox_ConnectionString.Text;
            }
        }

        private void Save_Click(object sender, EventArgs e)
        {
            Save();
        }

        private void button_Exit_Click(object sender, EventArgs e)
        {
            if (CheckSaveChanges() != DialogResult.Cancel)
            {
                if(cn!=null)
                    cn.Close();
                Close();
            }
        }

        private DialogResult CheckSaveChanges()
        {
            DialogResult dr;
            if (IsChaned())
            {
                dr = MessageBox.Show("Save changes?", "", MessageBoxButtons.YesNoCancel);
                if (dr == DialogResult.Yes)
                {
                    if (!Save())
                        return DialogResult.Cancel;
                }
                return dr;
            }
            else
                return DialogResult.No;
        }

        private bool Save()
        {
            try
            {
                SqlCeCommandBuilder cb = new SqlCeCommandBuilder(da);
                da.Update(ds, TableName);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString(), "Error");
                return false;
            }
            return true;
        }

        private bool IsChaned()
        {
            return ds.HasChanges();
        }

        private void button_Cell_Get_Click(object sender, EventArgs e)
        {
            try
            {
                int c = int.Parse(textBox_cell_col.Text);
                int r = int.Parse(textBox_cell_row.Text);
                textBox_Cell_value.Text = ds.Tables[TableName].Rows[r][c].ToString();
            }
            catch { }
        }

        private void button_Cell_Set_Click(object sender, EventArgs e)
        {
            try
            {
                int c = int.Parse(textBox_cell_col.Text);
                int r = int.Parse(textBox_cell_row.Text);
                ds.Tables[0].Rows[r][c] = textBox_Cell_value.Text;
            }
            catch { }
        }

        private void RunSQLCommand(string query)
        {
            try
            {
                SqlCeCommand cmd = new SqlCeCommand(query, cn);
                cmd.Connection.Open();
                cmd.ExecuteNonQuery();
                cmd.Connection.Dispose();
                cmd.Connection = null;
            }
            catch (SqlCeException ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
    }
}