Develop Reference

Building An App With Plug-in Support

I'm starting a new project which would greatly benefit from program add-ons. The program in its most basic form reads data from a serial port and parses it into database records. Examples of add-ons that could be written would be an auto-archive add-on, an add-on to filter records, etc. I'm writing both the program and the add-ons, but some customers need custom solutions, so instead of branching off and making a completely separate program, add-ons would be great. The simplest add-on would probably be a form who's constructor takes an object reference, manipulates the object in some way, then closes.
Unfortunately, I have absolutely no idea where to start coding, and almost as little idea where to search. Everything I search for turns up browser add-ons. From what I have gathered, I need to look into dynamic loading DLLs. Besides that, I'm clueless. Does anyone have any good resources or examples I that they know of?
I'm happy to provide more details, but this project is in its inception, so I don't have a ton of specific details (specifics kind of defeats the point of add-ons, too.)

You should seriously consider using the Managed Extensibility Framework (MEF) to handle your plugin architecture. It requires thinking about things a little differently, but it is well worth the mind-stretch.

This is a simple example to illustrate the basic technique.
codeproject.com - Plugin Architecture using C#
This article demonstrates to you how
to incorporate ... as a
plugin for another application or use
it as a standalone application.
in .NET 4 you now have the Managed Extensibility Framework (MEF) to do much of the plumbing.
In .NET 3.5 you had the System.AddIn but it was deemed by many to be far too complex.
codeproject.com - AddIn Enabled Applications with System.AddIn
AddIns (sometimes called Plugins) are
seperately compiled components that an
application can locate, load and make
use of at runtime (dynamically). An
application that has been designed to
use AddIns can be enhanced (by
developing more AddIns) without the
need for the orginal application to be
modified or recompiled and tested

You really need to look at Managed Extensibility Framework (MEF). This is specifically designed to help support add-ons and other extensibility.

A very basic description (basically, your plugins must implement a special interface):
http://martinfowler.com/eaaCatalog/plugin.html
Much better article, in C#:
http://www.drdobbs.com/184403942;jsessionid=TVLM2PGYFZZB1QE1GHPCKHWATMY32JVN

I think Reflection will play a major role.
I expirimented with an app that had a plugin folder. A filesystem watcher would watch the folder, and when a new DLL was placed in it, it would use reflection to determine which types of plugins it included, loaded them, and added them to the list of available classes, etc.

Try using the term 'add-in' or 'plug-in' for your research instead of 'add-on'. That should help some.
If you're using .Net 4, there's an add-in namespace in the framework that will get you partway there.
Writing plug-in support for an app is no simple task. You'll have to maintain pretty strict separation-of-concerns across your interfaces, you'll need to provide an interop library that defines ALL of the supported plug-in types, and you'll want to do some research into dependency injection & inversion of control, in addition to the previously-suggested reflection research.
It sounds like you might have a busy weekend doing research.

What is Silverlight? (In one sentence, in an interview)

Consider you are in an interview for a .NET/C# job, and are asked:
What is Silverlight, in one sentence?
EDIT: OK, some took it the funny way:-) I have accepted one of the more serious approaches though. However, thanks to all posters.

Microsoft Flash.

It's a framework for building interactive applications for the web, desktop, and mobile devices using .NET technologies.

This is my own try:
It's .NET in a browser.

Microsoft found the the way Java Applets should have worked.

Silverlight is a cross-platform approach for usable user interfaces within a browser.

It's Microsoft's answer to Adobe Flash, but its more powerful as it can utilise the rest of the .NET framework.

I would say something like ...
Microsofts aproach at embedding a lightweight version of the .Net framework in to a portable package that can be deployed on many platforms, this is often compared to flash of java as they also take the same aproach, essentially the idea is to allow the .Net platform to reach other areas where a full install would not be required / suitable.
... or ...
Its a cut down version of WPF designed to run on any platform with a lightweight deploy.

Simple answer is that it is a compact edition of WPF.

Silverlight is microsofts way of making flashy applications. Ops, was that a pun?

Vector-based animations and RIA based ond XAML and .NET.

Microsoft Silverlight is yet an another fad into web2.0 casket.

Silver light is a new cross-browser, cross-platform implementation of the .NET Framework for building and delivering the next generation of media experiences and Rich Interactive Applications(RIA) for the web. It runs in all popular browsers.It is combination of different technologies into a single development platform that allows you to select tools and the programming language you want to use. Silver light integrates seamlessly with your existing JavaScript and ASP.NET AJAX code to complement functionality which you have already created.

Are there any drawbacks to learning C# in MonoDevelop?

I want to learn C# because... It seems to be a pretty marketable language these days. More than C, not so much as PHP/MySQL in my area, but I'd rather be a software developer than a web developer. Anyways, I'm running linux, and I have no hope of working on a windows platform until I buy a new computer. So, are there any drawbacks to learning C# under linux? If so, are there any good lessons online for doing such a thing? Any good tutorials online for learning C# in general?
update
so what I'm getting is that the main drawback is that although the full C# language spec is implemented in mono, the full .Net framework isn't. But, until I can get a new system and run windows, I guess lacking the full framework will have to do.

The language spec is fully implemented but the framework itself is not. So learning C# the language will be no different (ignoring the benefits of using visual studio as your IDE). Writing against the framework will be a bit different.
edit> It also depends on what kind of programming you intend to do. Much of the parts of mono that aren't complete are also often edge cases for beginners that you aren't likely to run into. So if you're just learning C#, there's a very good chance that you won't come across the parts of the framework that haven't been implemented yet (and I mean yet, they are very fast at updating mono from what I've seen so far, so by the time you're ready to really explore the framework and all that it entails, there's a good chance that it might be completed by then)

learning C# on linux may actually be good, when you start doing it on windows, you will know both. The IDE will not be as modern, but I'll bet there are not many people that can do it on both.
You'll be able to concentrate on the actual C# language and you can learn the microsoft IDE when you get to use C# on windows.

The major drawbacks that I see are:
The latest .NET versions are not supported
Different tools between Mono and Visual Studio
In spite of that, I think you can learn a lot about C# on Mono.

Any good tutorials online for learning C# in general?
Here's a tutorial I wrote:
http://www.csharp-station.com/Tutorial.aspx
Feedback has indicated that all of the code in the tutorial runs fine on Mono.
Joe

Learning the language should not hurt, I would not depend on it to land you a job. However, keep in mind that many of the runtime services that are accessed via C# may not be available. Knowledge of those services is perhaps just as, if not more, important the language itself.

The main problem with C# on Linux is that your development system will not be as good, in most people's estimation. But you may get really good at vi(1)...

On MonoDevelop you won't have all the newest features of the .NET framework, it's somewhere between 2.0 and 3.5.
It supports C#3.0 though.

Mono is gaining traction very, very quickly. I've heard rumblings that MS is silently supporting Mono (see their approach with getting SL to run on Linux). In some cases, mono actually outperforms .net on a windows based server.
The downside would be the IDE and features, as many have already mentioned. Visual Studio is by far the best IDE out there.
It does support Asp.Net MVC IIRC though.

Mono overcomes the single biggest drawback to using .NET from Microsoft for many developers, the requirement to run on the Windows platform. By bringing the shared source release of the .NET Framework to multiple platforms and then building an open source project around extending it, The Mono Project has made the strengths of .NET available to a wide range of developers. The ability to develop using a variety of languages, all using a common interface and deployable on a number of platforms is a very compelling development strategy.
As far as the web services aspects of Mono are concerned, nearly all of the Framework is complete meaning a developer can begin developing web services today using Mono. Mono features nearly complete implementations of ASP.NET, ADO.NET and Web Forms, along with almost all of the SYSTEM namespace. For more a detailed visit mono's official site,mono-project.com check out these articles on Cool Solutions for Developers:

Well there is nothing wrong if we learn something & probably we might end up improving it which will be more useful to the future users.Probably that is the power of open source.I think all developers will agree to this point :)

Is WPF on Linux (already) possible?

I love programming with .NET, especially C# 3.0, .NET 3.5 and WPF. But what I especially like is that with Mono .NET is really platform-independent.
Now I heard about the Olive Project in Mono. I couldn't find some kind of Beta.
Does it already work? Have any of you made any experiences with it?
Edit: I know about Moonlight. But I want a standalone WPF application. And because of Moonlight I hope WPF on Linux will become true.

You'll have better luck working with Moonlight, which targets the Silverlight API, which is a subset of full WPF.
edit: Sure, Silverlight isn't "intended" for the desktop, but there's no reason why you can't embed a silverlight engine in your application. It's been done before, such as for the Mac NY Times Reader
more edit: see Miguel's post on Standalone Silverlight Applications

Update: Since people keep upvoting this, I want to point out it is long since out of date. Mono got acquired by MS years ago, and their posture regarding open-source has changed, so consider this post obsolete. (As obsolete as the WPF framework itself, heh).
Mono is in a bit of an uncomfortable position when it comes to Microsoft APIs such as Winforms and WPF. A subset of the .Net technology is an ECMA standard, but free implementations of these APIs are probably on shakier legal ground. I believe this was a large factor in the covenant between Novell and Microsoft, which is good for Novell customers. But people who use Mono that aren't customers of Novell aren't protected. For this reason a lot of people in the F/OSS community look askance at Mono despite its technical merits.
For this reason, Gtk# will always be preferred, since it is truly Free. Many people consider it to be superior to Winforms anyway. As far as WPF is concerned, it will almost certainly be a low priority for Novell. They may implement it eventually, but I would expect Moonlight to be the closest you could get for the forseeable future.
Since posting this, Microsoft has extended their covenant to anybody who implements the ECMA 334 & 335 standards.

From the mono website
At this point, the Mono project does
not have plans to implement Windows
Presentation Foundation APIs as
part of the project.
Moonlight is an implementation of silverlight, which is a browser based flash like technology based on a subset of WPF.
In my opinion the choice to not implement WPF is monos biggest mistake. As WPF is fast becoming the default choice for new .net user interfaces. See this blog for more.

There is a library called Silverform SDK that aims to provide cross-platform WPF and Silverlight implementation.
The library is implemented in managed code and currently works with OpenTK and Unity3D as render backends. Major functionality, such as binding, layout, main controls and primitives, has already been implemented (check Unity web player demos here). Initially it has been focused on Unity3d render, while support for standalone Mono applications will be added as a separate build in the future.
Disclaimer: I am one of the developers of the library.

If you check Known bugs of this link(also includes steps needed to install .NET onto Ubuntu)or this you may find that some(may be buggy) version of WPF works on Wine as for now. I did not find any definite test done as for now, but worth to try to run WPF "Hello world".
UPDATE2:
I have run latest IlSpy on latest Wine for Ubuntu 16.04. With 32 bit version of dotnet45 and corefonts installed via winetricks with windows 7 compatibility.
For this time no crashes and all things work fine. Fonts look really good.
IlSpy is shown via WPF and for person who loves programming with .NET is essential tool - the decompiler.
I downloaded latest portable SharpDevelop(build using WPF) with no extra. It started. Failed to create WPF project. Created WinForms. After opening some cs files and evidencing some glitches, tried to type - and it crashed.
UPDATE
I followed steps and got latest ILSpy.exe running on Ubuntu 14.4.
Next items to note:
wine stated that dotnet40 is not supported by 64 configuration, changed to 32 bit
fonts are ugly, but readable
basic functional works fine - I can see decompiled code - which is good enough for some development, but View -> Search and View -> Options -> Display crash.
Conclusion:
WPF on Linux is possible. But need some way to tackle issues.

From the Olive home page:
Olive is unsupported, should be
considered as experimental software,
and since it implements a shifting API
there are no guarantees of any kind
about the stability of the API.
I doubt anyone would have used it in a real project.

Yes, it is possible using NoesisGUI a real-time multi-platform XAML implementation. There are a few games already released using this technology in Linux, like VoidExpanse
Disclosure: I am one of the developers of this product.

I heard a podcast interviewing miguel de icaza (the mono lead) maybe a few weeks ago, so that would have been maybe mid-december 2008, and he said that they had no WPF support at all yet.

Theoretically, a stripped version of WPF COULD be compiled against WinPR or LibWine to run on Linux.
Currently there is no such setup, so someone would need to make one. Hopefully this might change soon.
As of running against or in a full Wine environment, I think that is seriously overkill and will result in too much bloat to be worth making a very small number of additional programs work.

Making a C#/Winform application cross-platform - should I use AIR, Mono, or something else?

I have an app that I've written in C#/WinForms (my little app). To make it cross-platform, I'm thinking of redoing it in Adobe AIR. Are there any arguments in favor of WinForms as a cross-platform app? Is there a cross-platform future for Winforms (e.g., Mono, etc.)? Suggestions for cross-platform UI development?
By cross-platform I mean, currently, Mac OSX, Windows and Linux.
This question was asked again and answered with better success.

As far as my experience in Flex/AIR/Flash actionscripting goes, Adobe AIR development environment and coding/debugging toolsets are far inferior to the Visual Studio and .NET SDK as of the moment. The UI toolsets are superior though.
But as you already have a working C# code, porting it to ActionScript might requires a redesign due to ActionScript having a different way of thinking/programming, they use different primitive data types, for example, they use just a Number instead of int float double etc. and the debugging tools are quiet lacking compared to VS IMO.
And I heard that Mono's GtkSharp is quiet a decent platform.
But if you don't mind the coding/debugging tooling problems, then AIR is a great platform. I like how Adobe integrates the Flash experience into it e.g. you can start an installation of AIR application via a button click in a flash movieclip, that kind of integration.

I'm thinking of redoing it in Adobe AIR
Not having spent much time with AIR, my personal opinion is that it is best for bringing a webapp to the desktop and provide a shell to it or run your existing flash/flex project on the desktop.
Btw, if you don't know ActionScript, I mean its details, quirks, etc, don't forget to factor in the time it will take googling for answers.
Are there any arguments in favor of WinForms as a cross-platform app?
Is there a cross-platform future for Winforms (e.g., Mono, etc.)?
It's always hard to predict what will happen, but there is at least one project (Plastic SCM) I know of which uses Mono Winforms on Win, Mac and Linux, so it is certainly doable. However, they say they built most of their controls from the ground up (and claim they want to release them as open source, but not sure if or when), so you will need to put in some work to make things look "pretty".
I played with Winforms on non-windows platforms and unfortunately, it isn't exactly "mature" (especially on Mac). So what you get out of the box may or may not be sufficient for your needs.
If you decide a desktop app is not the best way to provide a cross-platform solution, you can always take your business logic written in C# and create either a full-blown webapp with ASP.NET or go with Silverlight, so many other options exist with C#.

WinForms are fully supported by Mono, so they are cross-platform.

Why would you go with Air?
Use GTK#, and you have a cross platform forms engine and you get to keep your C# code.

Well I think the only way to for cross-platform reliably with C# is Microsoft Silverlight, but is not really WinForms, and browser-based. Other than that, yes Mono is a chance.

If you want to use the .net Framework, Microsoft Silverlight is a good (the only?) choice. The browser does a good job as a shell, but you could also write your own application shell for it. For example, Scott Handelman mentions the NY Times Reader written in Silverlight and hostet on Cocoa on a Mac.

I don't think there is a future for WinForms at all. Since it appears to have been a stop-gap solution even in MSFT world ( a very thin wrapper around Win32). And virtually no changes seem to have been made to System.Windows.Forms in both .NET 3.0 and 3.5
</speculation>
I would use Java or Air.

I think that as long as you make sure that the business logic code you write is cross-platform (i.e. using backslashes in paths only works on Windows - forward slashes works on all OS's), then Mono shouldn't have major problems running an unmodified WinForms program. Just make sure you test for graphical glitches.

I asked a similar question last week. I've been using Mono all along, and have had no issues running the applications I compile to IL to run on SuSE linux (I usually run KDE) or windows, however, I've not gone out and got a mac yet to test it on. I will be soon, though, probably with in a couple weeks. But all and all development in Mono has been very good at creating application that will run on multiple platforms.