[SOLVED] Datagridview dragDrop move rows

Hi Mark,

the bug was logged as WJ-8140 is fixed in the latest release (1.3.44):

Best regards
Frank

I have updated the sample to use DGV.HitTest() instead of calculating the row. However the null reference exception is caused by a new regression in the DGV occurring when a row is removed and added back. It’s fixed in the the dev build that will be uploaded shortly.

http://wisej.s3.amazonaws.com/support/attachments/Wisej.DataGridDragDrop.zip

I just tried the sample in this ticket with the latest version and I am getting an object reference exception. Is this still the recommended way to do it? It looks like the error is in the framework.

Hi Gunter,

We added DataGridView.HitTest() to the current build, coming online later on today.

Best,

Luca

Hi Frank

Thanks for the code. I missed grid.PointToClient(Control.MousePosition).Y,

There are 2 bugs in the code:

1. Crash when dropping into area after last row of datagridview

private void dataGridView1_DragDrop(object sender, DragEventArgs e)
...
                if (dropRow == null)
                {
                    grid.Rows.Remove(dragRow);
                    grid.Rows.Add(dropRow);
                }
Should be changed to:

                if (dropRow == null)
                {
                    grid.Rows.Remove(dragRow);
                    grid.Rows.Add(dropRow);
                }
2. Crash when dropping on the column header

private DataGridViewRow GetDragRow(DataGridView grid)

  {
    var rowCount = grid.RowCount;
    var index = grid.FirstDisplayedRowIndex - 1;
 
    var position = grid.PointToClient(Control.MousePosition).Y;
 
    position -= grid.ColumnHeadersHeight;
    if (position < 0)
    {
      position = 1;
    }
    while (position > 0 && index < rowCount)
    {
      index++;
      if (grid.Rows[index].Visible)
        position -= grid.Rows[index].Height;
    }
 
    return grid.Rows[index];
  }
}

In this case the index = 1- and position < 0, so the while loop will never be executed,

the statement
return grid.Rows[index];
 crashes, because index = -1

can be changed to 
position -= grid.ColumnHeadersHeight;
if (position < 0)
{
  position = 1;
}
The position is moved to the first visible row, an the drop operation is done on the is row.