C#

<br />
private void dgResults_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)<br />
{<br />
<br />
	bool shift = (Control.ModifierKeys & Keys.Shift) == Keys.Shift;<br />
	bool ctrl = (Control.ModifierKeys & Keys.Control) == Keys.Control;<br />
<br />
	DataGrid.HitTestInfo hti = dgResults.HitTest(e.X,e.Y);<br />
	if (hti.Type == DataGrid.HitTestType.RowHeader)<br />
	{<br />
		if (dgResults.IsSelected(hti.Row))		// current row is already selected - might be start of a drag?<br />
		{<br />
			if (ctrl)<br />
			{<br />
				// ....<br />
				// Deal with ctrl click on an already selected row<br />
			}<br />
			else if (shift)<br />
			{<br />
				// ....<br />
				// Deal with shift click on an already selected row<br />
			}<br />
			else<br />
			{<br />
				// User mouse down on an already selected row the current row selection shouldn't be cleared until the<br />
				// Mouse up event but the control deselects all row except the current row as soon as the mouse button is<br />
				// held down. Restore all the selected rows (SelectedRows is a list of the indices of all previously selected rows)<br />
				foreach (int i in SelectedRows)<br />
				{<br />
					dgResults.Select(i);<br />
				}<br />
			}<br />
		}	<br />
		else									<br />
		{<br />
			// ....<br />
			// Deal with rows that aren't already selected<br />
		}<br />
	}<br />
}<br />