Mobile

public partial class Form1 : Form
    {
       static SqlCeConnection _connection = null;
       public static SqlCeConnection Connection
        {
            get
            {
                if (_connection == null)
                {
                    _connection = new SqlCeConnection(ConnectionString);
                    _connection.Open();
                }
                return _connection;
            }
        }
        public Form1()
        {
            InitializeComponent();
        }
        public static DataSet ds = new DataSet();
        public static int rowindex = -1;
        private void menuExit_Click(object sender, EventArgs e)
        {
            Close();
        }
    

        #region File & Database Details

       static string CurrentFolder
        {
            get { return Path.GetDirectoryName(Assembly.GetExecutingAssembly().GetName().CodeBase); }
        }

        const string _databaseLocalFileName = "DB1.sdf";
       static string DatabasePathName
        {
            get { return Path.Combine(CurrentFolder, _databaseLocalFileName); }
        }

        const string _baseConnectionString = "Data Source =";
       static string ConnectionString
        {
            get { return _baseConnectionString + DatabasePathName; }
        }

        #endregion

        private void menuedit_Click(object sender, EventArgs e)
        {          
            rowindex = dataGrid1.CurrentRowIndex;
            if (dataGrid1.DataSource != null)
            {
                panel1.Visible = true;
                txtcol1.Text = ds.Tables[0].Rows[rowindex].ItemArray[0].ToString();
                txtcol2.Text = ds.Tables[0].Rows[rowindex].ItemArray[1].ToString();
                txttblID.Text = ds.Tables[0].Rows[rowindex].ItemArray[2].ToString();
            }
            else
                MessageBox.Show("should load data grid first", "error", MessageBoxButtons.OK, MessageBoxIcon.Hand, MessageBoxDefaultButton.Button1);
        }
        public static SqlCeDataAdapter adap;
        

        private void btnsave_Click_1(object sender, EventArgs e)
        {
            try
            {
                SqlCeCommand cmdUpdate = Connection.CreateCommand();
                SqlCeTransaction se = Connection.BeginTransaction();
                cmdUpdate.CommandType = CommandType.Text;
                cmdUpdate.CommandText = "UPDATE tbl SET Col1=@Col1, Col2=@Col2 where tblID = @tblID";
                cmdUpdate.Parameters.AddWithValue("@Col1", txtcol1.Text);
                cmdUpdate.Parameters.AddWithValue("@Col2", txtcol2.Text);
                cmdUpdate.Parameters.AddWithValue("@tblID", txttblID.Text);
                if (Connection.State != ConnectionState.Open)
                {
                    Connection.Open();
                }
                cmdUpdate.Transaction = se;
                cmdUpdate.ExecuteScalar();
                se.Commit(CommitMode.Immediate);
                Connection.Close();
                panel1.Visible = false;
                menuItem1_Click(null, null);
            }
            catch (SqlCeException ex)
            {
                throw ex;
            }
        }

        private void menuLoad_Click(object sender, EventArgs e)
        {
            try
            {
                SqlCeCommand com = new SqlCeCommand("Select * from Tbl ", Connection);
                adap = new SqlCeDataAdapter(com);
                if (ds.Tables.Count > 0)
                {
                    ds.Tables["tbl"].Clear();
                }
                adap.Fill(ds, "tbl");
                dataGrid1.DataSource = ds.Tables[0];
                adap.Dispose();
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }       
    }

<br />
        [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]<br />
        [global::System.ComponentModel.DataObjectMethodAttribute(global::System.ComponentModel.DataObjectMethodType.Fill, true)]<br />
        public virtual int Fill(AppDatabase1DataSet.testDataTable dataTable) {<br />
            this.Adapter.SelectCommand = this.CommandCollection[0];<br />
            if ((this.ClearBeforeFill == true)) {<br />
                dataTable.Clear();<br />
            }<br />
            int returnValue = this.Adapter.Fill(dataTable); // here the error<br />
            return returnValue;<br />
        }