Share an instance between multiple projects

Question

I am working in VS 2008 C# and need to share an instance of an object created in one project with another project. I tried creating a static class in project1 and adding it as a link to project2, but the information wasn't saved. The static class was written in project1.

//object o = new object
//project1.staticObject = o
//project2.object = project1.staticObject

When I tried something like above, project2.object would be null. By adding a class as a link, is it creating a new instance of the static class in project2 or is it referencing the same class? If it is referencing the same class, shouldn't any information saved into the static class from project1 be accessible by project2? I know this isn't the most elegant manner of sharing data, but if anyone would help with this problem or provide a better manner of doing it, I would greatly appreciate it.

Thanks in advance.

Answer 1

Projects run in separate processes, so they can't share data in this manner. You'll need to persist the data in another type of store. I recommend using a database (hey, 20 gazillion websites, stock trading apps, airlines, etc can't be wrong).

If you don't want to use a database, you could open an IP connection between instances of the app and have a thread send packets of data to sync back and forth between the applications. Or, in your "server" app, add a web service that each process would call to update and retrieve information.

If you need really high-speed communication between the processes, sockets with a peer or star topology is a good way to go. If you're okay with some latency, having a web service (which works fine even if these aren't web apps) or a database could be a good solution. The right approach depends on your application.

WCF could also solve this problem. It effectively wraps the IP/socket layer and provides some nice object persistence/remote control capabilities, but I find it overly complex for most applications.

Answer 2

To share a single instance of an object among different processes (that's what I think you are intending to do) you need something that will maintain that object's state. You can look at the WCF and how to set up it's behaviour to act as a singleton so essentially every requester gets the same instance across the board.

http://msdn.microsoft.com/en-us/magazine/cc163590.aspx

Answer 3

Creating the link creates only applies to the source code. When you compile each project, it then has that single class definition available in both projects. The process you took does nothing for instances during runtime for sharing.

You can look at WCF or .NET Remoting , although .NET Remoting is now officially replaced by WCF.

Answer 4

If you are talking about sharing the same object between two processes, you can do that, the concept is called memory-mapped files. Here is some starter docs from msdn.

Though the docs and API use the term "FileMapping" quite a bit, you can use it just for sharing memory between two processes.

In .NET 4.0, you can use the System.IO.MemoryMappedFiles namespace. For your case, looks like .NET 3.5, you'll have to use some sort of interop to use the Win API.