Question

I am having the following problem. I have a main project, and some extra projects that have similar functionality.

For example: I have an MVC website, then a class library project “A” with a “SettingsHelper”. This just defines static wrappers for configuration settings so they can be used as propertys.

Then I have another class library project “B”, which also contains a “SettingsHelper class”.

How can I merge these SettingsHelpers in my main project, so I can use: SettingsHelper.Property from both modular extra projects.

I would like to be able to plug extra class libraries into one project.

Answer 1

Sounds pretty much like Dependency Injection. Normally you would expose SettingsHelper as an interface (your contract), and program against that. Then a DI container, such as Ninject, StructureMap, or Windsor would plug an implementation of that interface into the relevant parts of your code based on configuration.

This would allow you to code against a known contract and provide different libraries depending on the circumstances, the DI framework could then use that library to get the concrete implementation of the interface.

Would you need both instances at the same time?

Note that you cannot utilise the partial keyword across different assemblies, only within an assembly.

Update: based on your comment it sounds like you want to do something like Composition. Have a class that takes both classes from either library and combines them into one class that can be used by your application. Whether you then configure it to do something special or load the types when the libraries are present, it can all be encapsulated in this new class.

Update 2: alternatively, look into MEF:

http://msdn.microsoft.com/en-us/library/dd460648.aspx