CODEWITHSUNDEEP
c#asp.net
Bill
Bill

Reputation: 2382

Implement partial methods across multiple assemblies

In one of the applications I am working on, there are two basic functionalities included: Create and Update.

However, there is a need sometimes to add custom code, so I thought of extending the code by allowing 3rd parties to write and embed their own code:

OnCreating OnCreated OnUpdating OnUpdated

Is there a way to enable the above across multiple assemblies? MEF might help here?

Thank you Regards

Thanks all for your replies.

Having such an interface means each external assembly has to implement that interface as needed. Then, my application's code, needs to loop through the currently running assemblies, detect all classes implementing that interface, and run their methods?

Does MEF fit here? I can export the implementation from external assemblies and import them inside my app?

Thank you Regards

Upvotes: 7

Views: 4747

Answers (7)

NepdeBrio
NepdeBrio

Reputation: 51

Partial classes across assemblies aren't supported because the concept behind the partial class is to allow multiple developers to contribute different methods and members for the same class under a particular namespace.
This was done in order to help developers to sync the code into a single class, inside one assembly, build after compilation.

Upvotes: 0

James Fernandes
James Fernandes

Reputation: 124

Regarding your MEF question, you could probably do something like the following to run methods from an interface:

var catalog = new DirectoryCatalog("bin");
var container = new CompositionContainer(catalog);
container.ComposeParts();

var plugins = container.GetExportedValues<IPlugin>();
foreach (IPlugin plugin in plugins)
{
    plugin.OnCreating();
}

Or create an interface with events as Brian Mains suggested:

public interface IPlugin 
{
    event OnCreatingEventHandler OnCreating;
}

then the above code would be more like:

var catalog = new DirectoryCatalog("bin");
var container = new CompositionContainer(catalog);
container.ComposeParts();

var plugins = container.GetExportedValues<IPlugin>();
foreach (IPlugin plugin in plugins)
{
    plugin.OnCreating += MyOnCreatingHandler;
}

I think I like the latter for the method names you specified. For my plugin work, I've created an interface similar to the following:

public interface IPlugin
{
    void Setup();
    void RegisterEntities();
    void SeedFactoryData();
}

The RegisterEntities() method extends the database schema at runtime, and the SeedFactoryData() method adds any default data (eg. adding default user, pre-population of Cities table, etc.).

Upvotes: 2

roeland
roeland

Reputation: 6336

You (or the user) can use extension methods: http://msdn.microsoft.com/en-us/library/bb383977.aspx

Upvotes: 1

Brian Mains
Brian Mains

Reputation: 50728

Consider using an interface:

IUpdatableObject<X>
   Creating(X obj);
   Created(X obj);
   Updating(X obj);
   Updated(X obj);

And then use this interface to add in custom code; each third party can implement this interface (well either they or you can through a wrapper) and this can be a tie into adding custom business logic.

HTH.

Upvotes: 1

Matthew Whited
Matthew Whited

Reputation: 22443

Partial methods and classes must be in the same assembly. Partial methods are compiled out if not used. If you need extension points for you classes you should look into virtual methods or events.

Upvotes: 0

Justin Niessner
Justin Niessner

Reputation: 245489

Having partial classes supported across assemblies isn't supported.

The reason being that all partial class definitions are combined into a single class during compile time. That single class resides in a single assembly.

Upvotes: 1

CodesInChaos
CodesInChaos

Reputation: 108880

You can't have partical classes accross assemblies because partial classes are a language feature, and not a CLR feature. The C# compiler merges all the partial classes into one real class, and that single class the the only thing left after compilation.

You have a couple of alternatives:

  1. Offer events
  2. Make the methods virtual and override them
  3. Use an interface

Your problem looks like it fits events best. The user can simply subscribe to them in the other assembly.

Upvotes: 14

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