Type mismatch with runtime loaded assembly

Question

I'm writing a plugin architecture for testing purposes (I know there are frameworks to do that), this is how I've done it right now:

I have a common library shared by the main program and the plugins dll, I'll call it PluginBase assembly.

That assembly is referenced in a plugin MyPlugin which is in the folder Debug\Plugins.

It is also referenced in the main program, which is in the folder Debug.

The problem is, when I dynamically load the interfaces contained in the PluginBase, it gets the interface's Type object from the assembly located in Debug\Plugins. But when I try to use the same interface (IMyPlugin) in the main program, it loads it from the PluginBase assembly located in the Debug folder.

And that causes invalid cast exceptions when I try to use the interface in the main Program.

The folder structure:

\Debug\MainProgram.exe
\Debug\PluginBase.dll
\Debug\Plugins\MyPlugin.dll
\Debug\Plugins\PluginBase.dll

The scenario of the loading is:

The ServiceProvider loads the plugins definition, ans also dynamically loads the interfaces contained in the PluginBase assembly (located in Debug\Plugins)
The main program calls the ServiceProvider to get a specific interface (but this time loaded from the Debug folder)
The types of the interfaces don't match (even if they are the same)....

I tried to locate the PluginBase dll in the Debug folder, but then I get compilation issues since the PluginBase dll gets copied to the Debug folder after the compilation of my plugin project. Also I don't think this is a clean way to do this.

Is there a way to overcome this problem ? (like perhaps setting a build order in a way?)

Are you trying to say that there is an `IMyPlugin` in both the PluginBase and MyPlugin projects? — Ron Beyer, Sep 04 '15 at 18:27
It's all about the SearchPath, look over here: http://stackoverflow.com/questions/1373100/how-to-add-folder-to-assembly-search-path-at-runtime-in-net — Jeroen van Langen, Sep 04 '15 at 18:30
Set the reference for PluginBase in the MyPlugin project to not copy to the output directory. — Ron Beyer, Sep 04 '15 at 18:31
@JeroenvanLangen yep that's what I figured out, but then I have build order problem, should I just exclude the `MyPlugin` project from the solution? — ppetrov, Sep 04 '15 at 18:31
Also, even if I set not to have a local copy of the dll, when I build the `MyPlugin` project, it still makes a copy of that library.... — ppetrov, Sep 04 '15 at 18:37
I wouldn't place the plugins in a separated path. Else you should add the pluginbase.dll to the GAC (or create a custom resolver) — Jeroen van Langen, Sep 04 '15 at 18:42
@JeroenvanLangen Ok thanks, I'll see what I can do from here :) — ppetrov, Sep 04 '15 at 18:44

Type mismatch with runtime loaded assembly

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