Hi ppl,

I have a situation where a user can add a user control to another control (like a scratchpad) at runtime. I've done this by way of a context menu. The user selects to add a new item from the context menu and then clicks on the scratchpad where they want to create the new control.

All works fine.

I want a user to be able to establish a relationship between any two controls by dragging one instance to another.

The problem is that in OnDragEnter I am looking to see if the control being dragged is of the right type. Of course this means that as soon as I mouse down on the source control, the event fires and thinks I'm dragging it to itself. What I really need is someway of quizzing the source control, to make sure it isn't the same instance as the destinataion.

Some code attached.

Cheers

The following two methods are part of class TaskSketchPad
This is fired when the user adds a control to the scratchpad.

protected override void OnMouseDown(MouseEventArgs e) {
   if (e.Button == MouseButtons.Left){
       switch ( _state ){   
       case State.Inserting:
        TaskBox tb = new TaskBox("New", "");
        tb.Left = e.X;
        tb.Top = e.Y;
        tb.Width = 100;
        tb.Height = 18;
        tb.AllowDrop = true;
        tb.DragEnter += new DragEventHandler(TaskBox_DragEnter);
        this.Controls.Add(tb);
        ChangeState(State.Normal);
        break;
       }
    }
    base.OnMouseDown (e);
   }
}

The event handler

void TaskBox_DragEnter(object sender, DragEventArgs e) {
   if ( e.Data.GetDataPresent(typeof(TaskBox))) {
    e.Effect = DragDropEffects.Copy;
    TaskBox tb = (TaskBox)sender;
    tb.Text = "Copying"; // This is simply here so I can see the event firing visually
                            // The problem is that it fires on the source because the source
                            // is of the same type as the destination (and hence the if check is true
    tb.Invalidate();
   }
   else {
    e.Effect = DragDropEffects.None;
   }
}

And finally in the TaskBox class this method

protected override void OnMouseDown(MouseEventArgs e) {
   DoDragDrop(this, DragDropEffects.Copy);
   base.OnMouseDown (e);
}

So in effect when I drag any instance to another instance the source changes its text to "Copying". I need this event to fire only when the source is dragged to another instance.

I tried modiying the if statement in TaskBox_DragEnter() to
if (!e.Data.Equals(sender) && e.Data.GetDataPresent(typeof(TaskBox)))
, but no joy.

Any help greatly appreciated. 4am. I'm off to bed :)

Thanks
Simon Rigby
Scotland