Prior to AutoCAD 2009, PaletteSet is sealed class, e.g. it cannot be inherited as a base class to derive your own custom PaletteSet. Since AutoCAD 2009, PaletteSet class is not sealed any more. This opens a possiblity for our AutoCAD programmer to create a custom, generic PaletteSet UI container once, and develop pluggable palette based on business need and plug into the PaletteSet when needed (without any code change to the PaletteSet).
In this article, I'll show how to use interface to define a pluggable PaletteSet. Interface is commonly used to define a set operations/properties for different classes to implement. It is one of the OO programming basic concept and used in .NET programming very often. However, there are many AutoCAD programmers who may not be a professional software developers and may too focused on AutoCAD API itself and did not explore some "advanced" programming technique enough, such as using "Interface" to simplify development tasks.
For this article, I demonstrate how to use Interface to create a pluggable PaletteSet. In Visual Stadio 2008, I started a class library project called MyPaletteSet, which includes 3 code files.
First code file is a interface that defines Palette that will be hosted in the pluggable PaletteSet: IThePalette. Later, when creating a Win Form UserControl as Palette, the UserControl will implement the interface. This, no matter how do you design your UserControls and how different they would be, to the hosting PaletteSet, they all are IThePalette. That is, the hosting PaletteSet does not have knowledge of each individual UserControl it hosts, as long as the UserControl is an IThePalette.
Here is the code:
Second code file is the custom PaletteSet, derived from Autodesk.AutoCAD.Windows.PaletteSet. As aforementioned, it is only possible when you use AutoCAD 2009 or later.
Here is the code:
Pay attention to this line of code:
public event DocumentCollectionEventHandler DwgBecameCurrent;
and this line of code:
_dwgManager.DocumentBecameCurrent += new .......
Some of your Palettes may be designed to handle drawing based data. Since PaletteSet is a floating/modeless window, when current drawing changed in AutoCAD, the data shown in certain palette should be refreshed because of current drawing change (like AutoCAD's "Properties" window). Therefore, the this type of palette must be able to handle various events originally raised by DocumentCollection. So, here I simply handle the DocumentCollection events in the custom PaletteSet and bubble the events up. It is up to the individual Palette to subscribe the events when necessary. To simplfy the example, I only handle and raise the DocumentBecameCurrent event. In real production code, we could bubble up all the DocumentCollection events. The third code file is contains a static help method to create an instance of the custom PaletteSet. Here is the code:
That's it. Now we have a generic, pluggable PaletteSet. Build the project. From now on, when you want to build a suite of your own tools that have UI to be hosted in a PaletteSet, you can focus to the development of the Palette (Win Form UserControl) and never need to update the PaletteSet host and redeploy it. Let's see a couple of sample palettes. Sample 1: FirstPalette. Start a new class library command. It can be in the same solution as the "MyPaletteSet". But to better understand the "pluggable" nature, it is recommended to do this project in different solution. This will show that you can really focus on developing your Palette without having to update the PaletteSet at all. Once the project created, set reference to the DLL generated in "MyPaletteSet" project (MyPaletteSet.dll). Add a Win Form UserControl, called FirstPalette. It looks like:
Then add another class file into the project: FirstPaletteCommand. Here is the code:
Since I want this palette to show per-drawing based data, thus, I make this palette subscribe event "DwgBecameCurrent" raised by the hosting PaletteSet (MyPaletteSet). As you can see, no matter what UI components you place onto this palette (UserControl) and what code logic you will let this palette to execute, you can plug the palette into a common PaletteSet easily. New, let me create another palette: SecondPalette. Start a new class library project, called "SecondPaletteTool", set reference to "MyPaletteSet.dll". Add a Win Form UserControl, which looks like:
Notice that this palette does not subscribe event raised by hosting PaletteSet. Add a class into the project: SecondPaletteCommand:
As you can see, no matter how different the second palette from the first one, it can be plugged into MyPaletteSet in the same way, because, to MyPaletteSet, these 2 palettes are the same type: IMyPalette.
Now, start AutoCAD and "NETLOAD" the 2 palette projects (e.g. load FirstPaletteTool.dll and SecondPaletteTool.dll separately, as if the 2 DLLs are deployed and loaded separately). Enter command "StartFirst" and/or "StartSecond". You can see the corresponding palette will be shown in a common PaletteSet. If you open more than one drawings in AutoCAD and switch the active drawing, you can see the file name shown on the "First Palette" changes accordingly, because this palette handles DwgBecameCurrent event raised by the hosting PaletteSet.
From now on, whenever I want to develop a new AutoCAD tool that would have a modeless window as UI, I can go ahead to develop the UI as Win Form UserControl. Once it is done, I can simply plug it into the common hosting PaletteSet. Since the newly developed palette is in its own project, it can be deployed independently to all existing palettes, yet they are hosted in the same PaletteSet.
In the FirstPalette, I have to add "using Autodesk.AutoCAD.ApplicationServices;" because the palette has to comsume DocumentCollectionEventArgs in the DwgBecameCurrent event handler. In real development code, it is best practice to not let the UserControl to be tied to AutoCAD's dll. In this case, it is better to define my own custom EvenArgs and my own custom EventHandler in the MyPaletteSet project and use them to bubble up the various DocumentCollection events.
Update note: due to the original posted code format, a key part of the code did not show correctly, which were the topic of the comments below. Now I updated the code posting format and show the line of code in red, which was previously shown wrong. - Norman, 2011-01-03.