protected override void OnMouseDown(MouseEventArgs e)
{
// listen for mouse click or starting to drag
base.OnMouseDown(e);
if (AllowDragDrop)
{
int pickedImageIndex = GetImageIndex(e.Location);
// check with -1 to ignore when the user clicking to blank zone
if (pickedImageIndex > -1)
{
_dragItem = new DraggingItem(_imgs[pickedImageIndex], e.Location);
_dragItem.Index = pickedImageIndex;
}
}
}
protected override void OnMouseUp(MouseEventArgs e)
{
base.OnMouseUp(e);
// checkin if swap is needed
if (_dragItem != null && e.Location != _dragItem.PickedLocation)
{
int droppedIndex = GetImageIndex(e.Location);
// check if the user drag an image then drop into blank zone in grid view
// then move the dragged item into the end of image list
if (droppedIndex == -1 && this.Bounds.Contains(e.Location))
{
droppedIndex = _imgs.Count - 1;
}
// and only swap if the user doesn't click to another non-client rectangle
if (droppedIndex != -1)
{
// swap if picked != dropped
if (droppedIndex != _dragItem.Index)
{
_imgs[_dragItem.Index] = _imgs[droppedIndex];
_imgs[droppedIndex] = _dragItem.ItemRef;
}
}
ReDraw();
}
else // click
{
this.SelectedIndex = GetImageIndex(e.Location);
// in case click, change selected index to invoke index changed event
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
// perform click
if (OnImageClicked != null)
{
OnImageClicked(this, new ImageGridItemClickedEventArgs()
{
Index = this.SelectedIndex,
Image = _imgs[this.SelectedIndex].Original
});
}
}
}
// then un-link drag item
_dragItem = null;
}
