[C#] ช่วยหน่อยคร๊ จะทำการลบข้อมูลที่ซ้ำกันออกจาก datatable

SELECT DISTINCT Col1,Col2 FROM myTable

  private void Form1_Load(object sender, EventArgs e)
        {
            //defining the number of Column
            dataGridView1.ColumnCount = 3;
            //Adding Columns Name
            dataGridView1.Columns[0].Name = "Product ID";
            dataGridView1.Columns[1].Name = "Prduct Name";
            dataGridView1.Columns[2].Name = "Product Price";
            //Definging row
            string[] row = new string[] { "1", "Pen", "55.52" };
            //adding row to gridview
            dataGridView1.Rows.Add(row);

            row = new string[] { "2", "Pen", "40" };
            dataGridView1.Rows.Add(row);

            row = new string[] { "3", "Copy", "20" };
            dataGridView1.Rows.Add(row);
            row = new string[] { "4", "Copy", "20" };
            dataGridView1.Rows.Add(row);
            row = new string[] { "5", "Pencil", "120" };
            dataGridView1.Rows.Add(row);
        }
        private void button1_Click(object sender, EventArgs e)
        {
            Dictionary<string, int> dic = new Dictionary<string, int>();
            string cellValue = null;
            for (int i = 0; i <= dataGridView1.Rows.Count - 1; i++)
            {
                if (!dataGridView1.Rows[i].IsNewRow)
                {
                    cellValue = dataGridView1[1, i].Value.ToString();
                    if (!dic.ContainsKey(cellValue))
                    {
                        dic.Add(cellValue, 1);
                    }
                    else
                    {
                        dic[cellValue] += 1;
                    }
                }
            }

            StringBuilder sb = new StringBuilder();
            sb.AppendLine("Number of unique products:");
            foreach (KeyValuePair<string, int> keyvalue in dic)
            {
                sb.AppendLine(string.Format("{0}: {1}", keyvalue.Key, keyvalue.Value));
            }
            lblUniqueProducts.Text = sb.ToString();
            lblTotalProducts.Text = "No Of Total Products: "+dic.Count.ToString();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            decimal sum = 0;
            for (int i = 0; i < dataGridView1.Rows.Count; ++i)
            {
                decimal dec = 0;
                decimal.TryParse(this.dataGridView1[2, i].FormattedValue.ToString(), out dec);
                sum += dec;
            }
            sum = Math.Round(sum);
            lblTotalPrice.Text = "Total Amount: "+sum.ToString("0.00");
        }