将项目从 DataGridView 拖放到面板

Question

我在DataGridView 中搜索了拖放解决方案，但我发现的只是重新排序项目。

但是我有一个 DataGridView 绑定到使用 LINQ to Entities 的 SQL 服务器数据库并且重新排序不适用，我想要的只是从 DataGridView 中拖动一个项目并将其放在同一面板上形式。我该怎么做？

我发现允许重新排序的代码：

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

    private void dgvResult_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 = dgvResult.DoDragDrop(
                dgvResult.Rows[rowIndexFromMouseDown],
                DragDropEffects.Move);
            }
        }
    }

    private void dgvResult_MouseDown(object sender, MouseEventArgs e)
    {
        // Get the index of the item the mouse is below.
        rowIndexFromMouseDown = dgvResult.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 dgvResult_DragOver(object sender, DragEventArgs e)
    {
        e.Effect = DragDropEffects.Move;
    }

    private void dgvResult_DragDrop(object sender, DragEventArgs e)
    {
        // The mouse locations are relative to the screen, so they must be 
        // converted to client coordinates.
        Point clientPoint = dgvResult.PointToClient(new Point(e.X, e.Y));

        // Get the row index of the item the mouse is below. 
        rowIndexOfItemUnderMouseToDrop =
            dgvResult.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;
            dgvResult.Rows.RemoveAt(rowIndexFromMouseDown);
            dgvResult.Rows.Insert(rowIndexOfItemUnderMouseToDrop, rowToMove);

        }
    }

在DataGridView 内进行任何拖放操作都会引发异常：

除非 DataGridView 数据绑定到支持更改通知并允许删除的 IBindingList，否则无法以编程方式删除行。

Answer 1

你没有解释你想对Panel中的行做什么，所以我编了一些东西..

您要做的第一件事是设置面板的AllowDrop = true。 然后编写DragEnter 和DragDrop 事件的脚本：

private void panel1_DragEnter(object sender, DragEventArgs e)
{
    // we indicate that we allow dropping
    e.Effect = DragDropEffects.Copy;
}

private void panel1_DragDrop(object sender, DragEventArgs e)
{
    // the mousemove has packed a row as data, so we unpack it:
    DataGridViewRow row = e.Data.GetData( typeof(DataGridViewRow)) as DataGridViewRow;
    // not sure what to do with it - store it in the tag
    panel1.Tag = row;
    // let the paint show something
    panel1.Invalidate();
}

private void panel1_Paint(object sender, PaintEventArgs e)
{
    // if we hava data in the tag we cast them to DataGridViewRow..
    // ..and display the content of the 2nd cell
    if (panel1.Tag != null)
        e.Graphics.DrawString( ((DataGridViewRow)panel1.Tag).Cells[1].Value.ToString(), 
                                this.Font, Brushes.DarkRed, 8, 8);
}

请注意，您可以删除 dgvResult_DragDrop 和 dgvResult_DragOver 事件，因为我们不想放在 DGV 上。

当然，绘画动作几乎是随机的..