Inheritance for csharp listboxes for drag drop?

[Full NameEntry]

Hi all,

I'm new to csharp... learning it by muddling my way though examples.

In my current example, I'm trying to make a form with a bunch of
listboxes that have drag and drop enabled amongst them...

I found an example online in the form of a DragNDrop.cs file that I've
included in my project (attached below).

I also have a form with a listbox (one for now) that is defined like
this...

private System.Windows. Forms.ListBox listBox1;

I'm not sure how I go about making the new methods from the DragNDrop.cs
file part of the 'standard' listbox.

In my research, it seems like I should be extending
System.Windows. Forms.ListBox and classing from that, but the example
doesn't really seem to be going that way...

Should I call ListBoxDragNDro p() with each standard listbox instance? If
so, what would the syntax for that be & where should I place it? I've
tried various different tacts, but they've all resulted in build
failures...

Thanks!!!

using System;
using System.Collecti ons.Generic;
using System.Componen tModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows. Forms;
namespace SchedulingTool
{
public class ListBoxDragNDro p : ListBox
{
private int lastMouseUpItem Index = -1;
private bool isDropSource = false;

public ListBoxDragNDro p()
{
this.AllowDrop = true; //allow D&D
this.SelectionM ode = SelectionMode.O ne; //single
selection

DragDrop += new System.Windows. Forms.DragEvent Handler
(OnDragDrop);
DragEnter += new System.Windows. Forms.DragEvent Handler
(OnDragEnter);
MouseDown += new System.Windows. Forms.MouseEven tHandler
(OnMouseDown);
SelectedIndexCh anged += new System.EventHan dler
(OnSelectedInde xChanged);
}

private void OnDragDrop(obje ct sender, DragEventArgs e)
{
if (e.Effect == DragDropEffects .Copy)
{
Point point = this.PointToCli ent(new Point(e.X, e.Y));
int index = this.IndexFromP oint(point);
if (index > -1 && index < this.Items.Coun t)
Items.Insert(in dex, e.Data.GetData
(DataFormats.Te xt));
else
Items.Add(e.Dat a.GetData(DataF ormats.Text));
}
}

private void OnDragEnter(obj ect sender,
System.Windows. Forms.DragEvent Args e)
{
if (e.Data.GetData Present(DataFor mats.Text) && !isDropSource)
e.Effect = DragDropEffects .Copy;
else
e.Effect = DragDropEffects .None;
}

private void OnMouseDown(obj ect sender,
System.Windows. Forms.MouseEven tArgs e)
{
if (MouseButtons == MouseButtons.Le ft && SelectedIndex ==
lastMouseUpItem Index)
{
isDropSource = true;
DoDragDrop(Sele ctedItem, DragDropEffects .Copy);
isDropSource = false;
lastMouseUpItem Index = this.SelectedIn dex;
}
}

private void OnSelectedIndex Changed(object sender,
System.EventArg s e)
{
lastMouseUpItem Index = this.SelectedIn dex;
}
}
}

[Paul Cheetham]

Hi,

private System.Windows. Forms.ListBox listBox1;

Change this line to this:

private SchedulingTool. ListBoxDragNDro p listBox1;
You will also need to change the new statement to:

listBox1 = new SchedulingTool. ListBoxDragNDro p();
The ListBoxDragNDro p class is a descendant of the standard Listbox.
I would suggest reading up on Inheritance and PolyMorphism so you get a
better understanding of what is going on. (They may be about C++, but
it's good enough. You should be able to understand the syntax, and the
principles are the same.)
Paul Cheetham

P.S. It's polite to use a name when you post :-)

[Alex]

Thanks Paul!

That did it... I guess the ListBoxDragNDro p was the new class - I didn't
understand it that way initially.

Alex

Paul Cheetham <PA******@dsl.p ipex.com> wrote in news:#PHvtN6bGH A.1204
@TK2MSFTNGP02.p hx.gbl:

Hi,

private System.Windows. Forms.ListBox listBox1;

Change this line to this:

private SchedulingTool. ListBoxDragNDro p listBox1;
You will also need to change the new statement to:

listBox1 = new SchedulingTool. ListBoxDragNDro p();
The ListBoxDragNDro p class is a descendant of the standard Listbox.
I would suggest reading up on Inheritance and PolyMorphism so you get a
better understanding of what is going on. (They may be about C++, but
it's good enough. You should be able to understand the syntax, and the
principles are the same.)
Paul Cheetham

P.S. It's polite to use a name when you post :-)

[Alex]

....I have another question on the same topic now.

What I'd like to do is remove the item from the source listbox once it is
dropped into the target listbox.

Is there a way I can tell the result of the drag operation from the source
listbox in the OnMouseDown method, or do I need to message back to the
source listbox in some way?

If so, how would I do that across windows? Right now I have one window
with the listbox (now classed as ListBoxDragNDro p) and I start two
instances of the window from my control window. I'm not sure how to have
the target listbox invoke a method on the source listbox dynamically (ie,
be able to do this regardless of the number of listboxes)...?

Thanks again!

[Alex]

....I was trying to message back via the "sender" object in the the
OnDragDrop method, but it didn't seem like it has the methods of the source
listbox exposed though it...