how to clear datagridview rows and columns

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C#

i used below coding to store data from listitems to array.From array to datagridview.
when i click button data added successfully into datagridview from array., but if i click again the same data appear two times into datagridview., [two times same data]. how to avoid this

private void button1_Click(object sender, EventArgs e)
      {
          try
          {
              foreach (ListItem li2 in ch11.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              foreach (ListItem li2 in ch1.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              foreach (ListItem li2 in ch2.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              foreach (ListItem li2 in ch3.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }
              foreach (ListItem li2 in ch4.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }
              foreach (ListItem li2 in ch5.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              foreach (ListItem li2 in ch8.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              foreach (ListItem li2 in ch6.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              foreach (ListItem li2 in ch7.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }
              foreach (ListItem li2 in ch9.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }
              foreach (ListItem li2 in ch10.CheckedItems)
              {
                  total_items[items] = li2.Text;
                  items++;
              }

              dataGridView1.Rows.Clear();
              dataGridView1.Columns.Clear();
              dataGridView1.Columns.Add("Items", "Choosed Items");

              try
              {
                  for (int j = 0; j < items; j++)
                  {
                      dataGridView1.Rows.Add(total_items[j].ToString());
                  }
              }
              catch (Exception err)
              {
                  MessageBox.Show(err.Message);
              }

           }

          catch (SqlException err)
          {
              MessageBox.Show(err.Message);
          }
      }