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I have a winforms app. I give it to three clients and each one wants a small tweak or customization specific just to them. To accomplish this, I'd have to keep a separate version just for each client. I may wind up having many versions doing it this way. I thought dependency injection would be how to handle this but I hear you have to register your dependencies in the main method and you'd still have to add a reference to each clients DLL so I'd still need different versions. What is the preferred object oriented way to handle this? Any better ways to handle this?

user204588
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  • Sounds like you are not charging enough money for these customizations. – Hans Passant Apr 06 '12 at 17:50
  • Storage is cheap. The interface should be seperate from the business logic anyways. If they are asking for custom business logic, it should be a fork to begin with, I honestly don't understand the problem. – Security Hound Apr 06 '12 at 18:27

3 Answers3

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You can use a Plug-in patten to load assembly at runtime: (from link)

Separated Interface (476) is often used when application code runs in multiple runtime environments, each requiring different implementations of particular behavior.

Most DI frameworks provide this functionality. You can search at get lots of Examples for framework you choose - if you don't want to roll your own.

  1. Ninject
  2. MEF
Community
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Raj Ranjhan
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You can use a configuration file to configure your DI container, so that you can reuse the same binaries with different configuration files to implement the different customizations. But you need to be sure that you thoroughly test all of your different configurations. Slightly different versions of the same application are not trivial to maintain without causing unanticipated breaks.

David Nelson
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Depending on the nature of the customixations, you might be able to capture all relevant modifications into a distinct part of the project (as opposed to keeping them spread all-over the project). If you can (e.g. a filering functionality is provided by the client), you can then load a DLL dynamically (e.g. based on a config file) and allow the functions in the DLL to perform the necessary functionality that accomplishes the customization (based on parameters provided by the main code).

This way you provide pre-defined hooks to your code that can be changed dynamically (even if only to load the dlls at startup time) as per the need of the client. You can separate these DLLs into multiple ones if there are distinct features that the clients want to change, but not necessarily all of the clinets all of the features. Then you can provide a "default" version of the DLLs.

Who develops the hooks is dependent on your setup with the clients.

Make sure you provide adequate documentation on how these hooks supposed to work -- even if you end up developing them.

Attila
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