Help me with NullReferenceException, please?

Question

Hello, Please help me with this code. I am trying to retrieve data from my table row and I dont have a success for two days.

This is a piece of code, witch I think couse a trouble:

 private void ViewDataForm_Load(object sender, EventArgs e)
        {
            DataTable dt = new DataTable("NewTable");
            DataSet ds = new DataSet();
            ds.Tables.Add(dt);
            DataColumn column;

            column = new DataColumn();
            column.DataType = System.Type.GetType("System.Int32");
            column.ColumnName = "id";
            column.ReadOnly = true;
            column.Unique = true;
            dt.Columns.Add(column);

            dt.Columns.Add("Month", typeof(String));
            dt.Columns.Add("Balance", typeof(String));

            DataColumn[] PrimaryKeyColumns = new DataColumn[1];
            PrimaryKeyColumns[0] = dt.Columns["id"];
            dt.PrimaryKey = PrimaryKeyColumns;


            String sqlQuery = "";
            int counter = 0;

            System.Data.SqlServerCe.SqlCeConnection conn = new System.Data.SqlServerCe.SqlCeConnection(
                ("Data Source=newDB.sdf;Max Database Size=2047"));

            try
            {
                //Let's assing our sql data reader
                SqlCeDataReader myReader = null;

                // Let's connect to it
                conn.Open();
                System.Data.SqlServerCe.SqlCeCommand cmd = conn.CreateCommand();

                sqlQuery = "SELECT SUM(income-expense) AS Balance, date_y AS Date FROM Income WHERE date = '" + comboBoxCurrentlyShowingYear.SelectedItem + "' GROUP BY date_y ORDER BY " + comboBoxSortBy.SelectedItem + " " + comboBoxASCDESC.SelectedItem;
                cmd.CommandText = sqlQuery;
                myReader = cmd.ExecuteReader();

                while (myReader.Read())
                {
                    counter++;
                    dt.Rows.Add(counter, myReader[1].ToString(), myReader[0].ToString());
                }
                dataGridIncome.DataSource = ds.DefaultViewManager.CreateDataView(dt);

                int primaryKey = dataGridIncome.CurrentRowIndex + 1;

                DataRow findRow = ds.Tables[0].NewRow();

                findRow = dt.Rows.Find(primaryKey);

                //!#!#! I get a message after that Message.Show() method. It says:  NullReferenceException was unhandled. !#!#!
                MessageBox.Show("Current row index: " + findRow[0].ToString() + "\nMonth: " + findRow[1].ToString() + "\nBalance: " + findRow[2].ToString());
            }
            finally
            {
                //Close that connection NOW
                conn.Close();
                ds.Tables.Clear();
            }
        }

I get an error after proceding Message.Show method.
If someone, please, can help me.