Question

Users drag rows up and down in my DataGridView. I have the dragging logic down-pat, but I’d like there to be a dark marker indicating where the row will be placed after I let go of the mouse.

Example from Microsoft Access http://img718.imageshack.us/img718/8171/accessdrag.png
Example from Microsoft Access; I want to drag rows instead of columns

Does anyone know how I’d go about doing this? Is this built-in, or would I have to draw my own marker (if so, how do I do that)?

Thanks!

Answer 1

I did this for a treeview a couple years ago; can’t remember exactly how, but consider using the MouseMove event of the DataGridView.

While the drag is occurring, your MouseMove handler should:

• get the relative coordinates of the
  mouse (the MouseEventArgs contains
  the coordinates, but I think they’re screen coordinates, so you can use DataGridView.PointToClient() to convert them to relative)
• determine which row is at that X
  position (is there a method for this? If not, you can calculate it by adding up the row + row header heights, but remember that the grid may have been scrolled)
• highlight that row or darken its
  border. One way you may be able to darken one border is by changing the DataGridViewRow.DividerHeight property.
• when the mouse moves outside that
  row, restore it to how it previously
  looked.

If you wanted to do something custom with the appearance of the row under the mouse (instead of just using the available properties), you can use the DataGridView.RowPostPaint event. If you implement a handler for this event which is only used when a row is being dragged over another row, you can repaint the top or bottom border of the row with a bolder brush. MSDN example here.