How could I Drag and Drop DataGridView Rows under each other?

Question

I've DataGridView that bound a List<myClass> and i sort it by "Priority" property in "myClass". So I want to drag an "DataGridViewRow" to certain position to change it's "Priority" property.

How could I "Drag & Drop" DataGridView Rows ?. And how to handle this ?.

Answer 1

I found this code sample on MSDN

Note the following:

1). DataGridView property AllowDrop must be set to true (default is false).

2). The example below works out of the box when the DataGridView is NOT data-bound. Otherwise it will throw an InvalidOperationException. If it is databound, you should manipulate the order of items in the DataSource.

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);

    }
}

Answer 2

The Answer from 'Wahid Bitar' helped me a lot. I cannot comment the above, so a small addition: If deleting a row is unwanted as commented by 'neminem': Just add to DragDrop Event just before the lines that finally moves it:

        if (rowIndexOfItemUnderMouseToDrop < 0 )
        {
            return;
        }        
       dataGridView1.Rows.RemoveAt(rowIndexFromMouseDown);
       dataGridView1.Rows.Insert(rowIndexOfItemUnderMouseToDrop, rowToMove);