Cancelling of Drag/Drop on DataGridView - vb.net

Question

I am using basic Drag/Drop functionality in single DataGridView.
Like this:
Private Sub DataGridView1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles DataGridView1.DragDrop
Dim p As Point = Me.PointToClient(New Point(e.X, e.Y))
dropindex = DataGridView1.HitTest(p.X, p.Y).RowIndex
If (e.Effect = DragDropEffects.Move) Then
Dim dragRow As DataGridViewRow = CType(e.Data.GetData(GetType(DataGridViewRow)), DataGridViewRow)
'' SOME PROCEDURE HERE FOR DROPPING ---
End If
End Sub
Private Sub DataGridView1_DragOver(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles DataGridView1.DragOver
e.Effect = DragDropEffects.Move
End Sub
Private Sub DataGridView1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles DataGridView1.MouseDown
dragindex = DataGridView1.HitTest(e.X, e.Y).RowIndex
If dragindex > -1 Then
Dim dragSize As Size = SystemInformation.DragSize
dragrect = New Rectangle(New Point(CInt(e.X - (dragSize.Width / 2)), CInt(e.Y - (dragSize.Height / 2))), dragSize)
Else
dragrect = Rectangle.Empty
End If
End Sub
Private Sub DataGridView1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles DataGridView1.MouseMove
If (e.Button And MouseButtons.Left) = MouseButtons.Left Then
If (dragrect <> Rectangle.Empty AndAlso Not dragrect.Contains(e.X, e.Y)) Then
Me.DoDragDrop(DataGridView1.Rows(dragindex), DragDropEffects.Move)
End If
End If
End Sub
When I push left mouse button and start to drag some square appears under a cursor and dragging begins.
If I release button on certain row dropping occurs (normally:)
But, if during dragging I change a mind and press ESC key those square under cursor dissappears but dropping occurs anyway when I release button.
What to do to cancel dropping when dragging already begins (say with ESC key)?

Answer 1

Me.DoDragDrop(DataGridView1.Rows(dragindex), DragDropEffects.Move)
You made a mistake there. The QueryContinueDrag event is raised on the control that called DoDragDrop(). You used Me, making the form the source of the data. But you implemented the QueryContinueDrag for DataGridView1, not the form. So your event handler never runs. Fix:
DataGridView1.DoDragDrop(DataGridView1.Rows(dragindex), DragDropEffects.Move)

Answer 2

You cannot track ESC by relying on the Key Event methods of the DataGridView, because are not triggered while you are drag-dropping. But there is an easy way to account for this situation (drag-drop process interrupted): DragLeave Event. You can make the condition for dropping depend upon a global flag set in this method. Sample code:
Dim cancelDrop As Boolean
Private Sub DataGridView1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles DataGridView1.DragDrop
Dim p As Point = Me.PointToClient(New Point(e.X, e.Y))
dropindex = DataGridView1.HitTest(p.X, p.Y).RowIndex
If (e.Effect = DragDropEffects.Move AndAlso Not cancelDrop) Then
Dim dragRow As DataGridViewRow = CType(e.Data.GetData(GetType(DataGridViewRow)), DataGridViewRow)
'' SOME PROCEDURE HERE FOR DROPPING ---
End If
cancelDrop = False
End Sub
Private Sub DataGridView1_DragLeave(sender As Object, e As System.EventArgs) Handles DataGridView1.DragLeave
cancelDrop = True
End Sub