DataGridView ソート禁止

        DataTable dt = new DataTable("MyTable");
        private void Form1_Load(object sender, EventArgs e)
        {
            for (int i = 0; i < 30; i++)
            {
                dt.Columns.Add(string.Format("ColName{0:d3}",i),typeof(string));
            }

            Random r = new Random();
            for (int i = 0; i < 100; i++)
            {
                DataRow dr = dt.NewRow();
                for (int ii = 0; ii < 30; ii++)
                {
                    dr[ii] = string.Format("Col{0:d3} - Value{1:d3}", ii,r.Next(100));
                }
                dt.Rows.Add(dr);
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            dataGridView1.DataSource = null;

            Stopwatch sw = new Stopwatch();
            sw.Start();

            dataGridView1.DataSource = dt;
            for (int i = 0; i < dataGridView1.Columns.Count; i++)
                dataGridView1.Columns[i].SortMode = DataGridViewColumnSortMode.Programmatic;

            sw.Stop();
            MessageBox.Show(string.Format("経過時間 : {0}ミリ秒", sw.ElapsedMilliseconds));

        }