title: Unselect all rows in datagridview
body: <p>I have two datagridviews, and when I click to one of them, I would like to deselect all selection in the second datagridview, I tried this, but nothing works:</p>
  
  <pre><code>firstItemsDataGridView.ClearSelection();
  firstItemsDataGridView.CurrentCell = null;
  </code></pre>
  
  <p>not working,</p>
  
  <pre><code>firstItemsDataGridView.ClearSelection();
  if (firstItemsDataGridView.Rows.Count &gt; 0)
      firstItemsDataGridView[1, 0].Selected = true;
  firstItemsDataGridView.CurrentCell = null;
  firstItemsDataGridView.ClearSelection();
  foreach (DataGridViewRow item in firstItemsDataGridView.Rows) {
      item.Selected = false;
  
      foreach (DataGridViewCell itemCell in firstItemsDataGridView.Columns) {
          itemCell.Selected = false;
      }
  }
  </code></pre>
  
  <p>not working,</p>
  
  <pre><code>firstItemsDataGridView.Rows[0,-1].Selected = true;
  </code></pre>
  
  <p>not working too.</p>
  
  <p>I have set selecting mode to full row selection, and I have no idea how to achieve my goal.<br> thanks a lot!</p>