如何在DataGridView中模仿Windows資源管理器多選/拖放行為？

Question

我試圖模仿Windows資源管理器處理多個選擇的方式。 在默認的DataGridView中，您可以使用Ctrl-單擊選擇多個項目。 但是，如果您釋放Ctrl鍵然后嘗試拖放所選項目，它將清除所選項目並僅選擇“點擊”行。 我在網上找到了以下解決方案。

protected override OnMouseDown(MouseEventArgs e)
{
  int hitRowIndex = HitTest(e.X, e.Y).RowIndex;
  if(!SelectedRows.Contains(Rows[hitRowIndex]))
  {
    base.OnMouseDown();
  }
}

但是，這會導致其他副作用。 按住CTRL鍵並將鼠標放在所選項目上，該項目保持選中狀態。 這是有道理的，因為如果選中了單擊的行，則會繞過mousedown事件。 從查看Windows資源管理器的行為看，在MouseUp事件之前，不會處理保留CTRL鍵的項目的取消選擇。 有沒有人試過這樣做？

Answer 1

我已經創建了一個自定義組件來解決這個問題，以及我在datagridview中進行多選的一些其他惱人的問題。 這是代碼，希望它可以幫助任何人：

public partial class CustomDataGridView : DataGridView
{
    public CustomDataGridView()
    {
        InitializeComponent();
    }
    public CustomDataGridView(IContainer container)
    {
        container.Add(this);

        InitializeComponent();
    }

    private bool _delayedMouseDown = false;
    private Rectangle _dragBoxFromMouseDown = Rectangle.Empty;

    private Func<object> _getDragData = null;
    public void EnableDragDrop(Func<object> getDragData)
    {
        _getDragData = getDragData;
    }

    protected override void OnCellMouseDown(DataGridViewCellMouseEventArgs e)
    {
        base.OnCellMouseDown(e);

        if (e.RowIndex >= 0 && e.Button == MouseButtons.Right)
        {
            var currentRow = this.CurrentRow.Index;
            var selectedRows = this.SelectedRows.OfType<DataGridViewRow>().ToList();
            var clickedRowSelected = this.Rows[e.RowIndex].Selected;

            this.CurrentCell = this.Rows[e.RowIndex].Cells[e.ColumnIndex];

            // Select previously selected rows, if control is down or the clicked row was already selected
            if ((Control.ModifierKeys & Keys.Control) != 0 || clickedRowSelected)
                selectedRows.ForEach(row => row.Selected = true);

            // Select a range of new rows, if shift key is down
            if ((Control.ModifierKeys & Keys.Shift) != 0)
                for (int i = currentRow; i != e.RowIndex; i += Math.Sign(e.RowIndex - currentRow))
                    this.Rows[i].Selected = true;
        }
    }
    protected override void OnMouseDown(MouseEventArgs e)
    {
        var rowIndex = base.HitTest(e.X, e.Y).RowIndex;
        _delayedMouseDown = (rowIndex >= 0 &&
            (SelectedRows.Contains(Rows[rowIndex]) || (ModifierKeys & Keys.Control) > 0));

        if (!_delayedMouseDown)
        {
            base.OnMouseDown(e);

            if (rowIndex >= 0)
            {
                // 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 datagridview.
                _dragBoxFromMouseDown = Rectangle.Empty;
        }
    }
    protected override void OnMouseUp(MouseEventArgs e)
    {
        // Perform the delayed mouse down before the mouse up
        if (_delayedMouseDown)
        {
            _delayedMouseDown = false;
            base.OnMouseDown(e);
        }

        base.OnMouseUp(e);
    }
    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);

        // If the mouse moves outside the rectangle, start the drag.
        if (_getDragData != null && (e.Button & MouseButtons.Left) > 0 &&
            _dragBoxFromMouseDown != Rectangle.Empty && !_dragBoxFromMouseDown.Contains(e.X, e.Y))
        {
            if (_delayedMouseDown)
            {
                _delayedMouseDown = false;
                if ((ModifierKeys & Keys.Control) > 0)
                    base.OnMouseDown(e);
            }

            // Proceed with the drag and drop, passing in the drag data
            var dragData = _getDragData();
            if (dragData != null)
                this.DoDragDrop(dragData, DragDropEffects.Move);
        }
    }
}

Answer 2

可能對此有所幫助：

    protected override void OnMouseDown(MouseEventArgs e)
    {
        int hitRowIndex = HitTest(e.X, e.Y).RowIndex;
        if ((!SelectedRows.Contains(Rows[hitRowIndex])) || ((ModifierKeys & Keys.Control) != Keys.None))
        {
            base.OnMouseDown(e);
        }
    }