CODEWITHSUNDEEP
c#
David Arno
David Arno

Reputation: 43254

Is there a way to express a generic handler in a generic way in C#?

Imagine I have an interface that specifies some collection handler:

interface ICollectionHandler<T> where T : new() { ... }

I then have same other class that wants a collection handler, which it will use for various types, so I want to do something like:

class SomeClass<T> where T : ICollectionHandler<> ...

If I do this though, I get an error saying that the "Type argument is missing".

So is there a way of specifying that T is a generic type, whose own type argument can be specified at runtime, or am I pushing C# beyond its (possibly sensible) boundaries here?

Upvotes: 3

Views: 253

Answers (3)

Dennis Traub
Dennis Traub

Reputation: 51634

You can create a base interface for ICollectionHandler<T> and constrain against it.

interface ICollectionHandler { ... }
interface ICollectionHandler<T> : ICollectionHandler where T : new() { ... }
class SomeClass<T> where T : ICollectionHandler { ... }

Or add a parameter to SomeClass representing the Type that should be passed into the ICollectionHandler<T> constraint:

class SomeClass<T, U> where T : ICollectionHandler<U> { ... }

Upvotes: 3

LightStriker
LightStriker

Reputation: 21004

You could try something like:

interface ICollectionHandler<T> where T : new() { }

public class MyImplementation<T, U> where T : ICollectionHandler<U> { }

I'm pretty sure that knowing which generic type reside inside your implementation of your interface is required. If you don't care about that sub-type:

interface ICollectionHandler { }

public abstract class CollectionHandler<T> : ICollectionHandler where T : new()  { }

public class MyImplementation<T> where T : ICollectionHandler { }

But it really depends how you are gonna use that and in what context. Maybe you can give more details?

Upvotes: 5

kevingessner
kevingessner

Reputation: 18985

You can add a second type parameter to SomeClass:

class SomeClass<T, U> where T : ICollectionHandler<U> ...

Upvotes: 2

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