当鼠标按住单元格时，如何在 DataGridView 中维护选定的行？

我正在尝试在 DataGridView 中实现行移动。我希望能够选择多行并单击任何选定行的单元格以开始拖动操作。问题是当我将鼠标放在单元格上时，行会被取消选择。我怎样才能防止这种情况发生？

通过快速的谷歌搜索，this http://social.msdn.microsoft.com/Forums/en-US/winforms/thread/9c38740d-be4a-4d50-99ef-1ac4c8c48d92似乎是自定义行拖放的解决方案。请注意，我刚刚从链接页面中删除了以下代码，我无法保证其有效性。

private Rectangle dragBoxFromMouseDown;
private int rowIndexFromMouseDown;
private int rowIndexOfItemUnderMouseToDrop;

private void dataGridView1_MouseMove(object sender, MouseEventArgs e)
{
    if ((e.Button & MouseButtons.Left) == MouseButtons.Left)
    {
        // If the mouse moves outside the rectangle, start the drag.
        if (dragBoxFromMouseDown != Rectangle.Empty &&
            !dragBoxFromMouseDown.Contains(e.X, e.Y))
        {
            // Proceed with the drag and drop, passing in the list item.                    
            DragDropEffects dropEffect = dataGridView1.DoDragDrop(dataGridView1.Rows[rowIndexFromMouseDown], DragDropEffects.Move);
        }
    }
}

private void dataGridView1_MouseDown(object sender, MouseEventArgs e)
{
    // Get the index of the item the mouse is below.
    rowIndexFromMouseDown = dataGridView1.HitTest(e.X, e.Y).RowIndex;

    if (rowIndexFromMouseDown != -1)
    {
        // Remember the point where the mouse down occurred. 
        // The DragSize indicates the size that the mouse can move 
        // before a drag event should be started.                
        Size dragSize = SystemInformation.DragSize;
        // Create a rectangle using the DragSize, with the mouse position being
        // at the center of the rectangle.
        dragBoxFromMouseDown = new Rectangle(new Point(e.X - (dragSize.Width / 2), e.Y - (dragSize.Height / 2)), dragSize);
    }
    else
    {
        // Reset the rectangle if the mouse is not over an item in the ListBox.
        dragBoxFromMouseDown = Rectangle.Empty;
    }
}

private void dataGridView1_DragOver(object sender, DragEventArgs e)
{
    e.Effect = DragDropEffects.Move;
}

private void dataGridView1_DragDrop(object sender, DragEventArgs e)
{
    // The mouse locations are relative to the screen, so they must be 
    // converted to client coordinates.
    Point clientPoint = dataGridView1.PointToClient(new Point(e.X, e.Y));
    // Get the row index of the item the mouse is below. 
    rowIndexOfItemUnderMouseToDrop = dataGridView1.HitTest(clientPoint.X, clientPoint.Y).RowIndex;
    // If the drag operation was a move then remove and insert the row.
    if (e.Effect== DragDropEffects.Move)
    {
        DataGridViewRow rowToMove = e.Data.GetData(typeof(DataGridViewRow)) as DataGridViewRow;
        dataGridView1.Rows.RemoveAt(rowIndexFromMouseDown);
        dataGridView1.Rows.Insert(rowIndexOfItemUnderMouseToDrop, rowToMove);
    }
}