'Dealing with optional dependencies (C#)

We have an app which optionally integrates with TFS, however as the integration is optional I obviously don't want to have all machine need the TFS assemblies as a requirement.

What should I do?

  1. Is it ok for me to reference the TFS libraries in my main assemblies and just make sure that I only reference TFS related objects when I'm using TFS integration.

  2. Alternatively the safer option would be to reference the TFS libraries in some separate "TFSWrapper" assembly:

    a. Is it then ok for me to reference that assembly directly (again as long as I'm careful about what I call)

    b. Should I instead be exposing a set of interfaces for my TFSWrapper assembly to implement, and then instantiate those objects using reflection when required.

1 seems risky to me, on the flip side 2b seems over-the-top - I would essentially be building a plug-in system.

Surely there must be a simpler way.

c++sharpdependencies


Solution 1:[1]

You might look at Managed Extensibility Framework (MEF).

Solution 2:[2]

A "plug-in" concept may be the way to go, and it may also allow you to (later) extend your application to work with other products than TFS if needed. Option 2a will be just as "risky" (failing when the linked files are missing) as option 1.

You can make an assembly with the required interfaces for your specific purpose, and reference this assembly from both your app and the "TFS plug-in". The latter then provides implementations of your interfaces and uses TFS to perform the operations. The app can dynamically load an assembly and create instances of the plug-in types needed (via Activator etc.) and cast those instances to your interfaces.

In fact, if you make those types inherit from MarshalByRef, you could even load them into another AppDomain and thus make a clean separation of your plugins, and also make them unloadable.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Mingwei Samuel
Solution 2 Lucero

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