c# - 如何在 DataGridView 中模仿 Windows 资源管理器的多选/拖放行为？

Question

我正在尝试模仿 Windows 资源管理器处理多项选择的方式。在默认的 DataGridView 中，您可以使用 Ctrl 键单击来选择多个项目。但是，如果您释放 Ctrl 键，然后尝试拖/放所选项目，它会清除所选项目并仅选择“命中”行。我在网上某处找到了以下解决方案。

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

但是，这会导致其他副作用。按住 CTRL 键并在所选项目上按住鼠标，该项目将保持选中状态。这是有道理的，因为如果选择了单击的行，则会绕过 mousedown 事件。从 Windows 资源管理器的行为来看，似乎直到 MouseUp 事件才处理取消选择按住 CTRL 键的项目。有没有人试过这样做？

Answer 1

我已经创建了一个自定义组件来解决这个问题，以及我在 datagridview 中的多选时遇到的一些其他烦人的问题。这是代码，希望对大家有帮助:

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);
        }
    }
}