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c#genericsinheritance
Elixir
Elixir

Reputation: 367

Generics with Lazy<T>

I am trying to understand the following.

Say I have a class:

public sealed class UsageClass<TInstance> : IConsumer<TInstance>
    where TInstance: Lazy<SomeClass>

Now say I want to inherit the lazyclass

public class ImplementationClass : SomeClass

Now when I try to do

UsageClass<ImplementationClass> instance = new UsageClass<ImplementationClass>();

I would get an error.

This leave me with a couple of options:

wrap TInstance in Lazy, which I do not want to do. I want the objects in the class to always be lazy.

Try and make Implementation class inherit Lazy which I do not think will work. Will the child class then be lazy? and I think the compiler will still complain.

So my question is. How do I successfully Inherit Lazy for use with generic classes given the constraints above?

Upvotes: 1

Views: 453

Answers (2)

Elixir
Elixir

Reputation: 367

To those interested I solved my issue by instead of making my classes Lazy I instead marked all my method properties inside the interface as lazy. This way I could still make my items of T and have lazy instantiation down the chain.

Upvotes: 0

Patrick Hofman
Patrick Hofman

Reputation: 156968

You can't do that because it can't inherit the SomeClass. TInstance is statically defined to be Lazy<SomeClass>, not Lazy<ImplementationClass>. No generic there. You have to adjust your UsageClass to make the Lazy use the generic type instead to be statically typed (thanks to Dennis_E for giving the right pointer):

public class UsageClass<TInstance> : IConsumer<Lazy<TInstance>>
                                     where TInstance : SomeClass

Then you can instantiate it like this:

UsageClass<ImplementationClass> instance = new UsageClass<ImplementationClass>();

Upvotes: 2

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