How to detect if a type is a Func<T> and get the type of the T [duplicate]

Question

I am wondering whether I can upgrade a basic IoC container I am using to support lazy load. So if I have registered IFoo, I would like the IoC container to know how to fulfil both of the following dependencies (the first being the standard way IoC containers work, while the second returns a simple delegate that calls into the container for an IFoo when it is invoked).

public Bar(IFoo x) public Bar2(Func<IFoo> lazyFoo)

The problem comes when I try to write the code that will actually do this. Is there a syntax that will make the following pseudo-code compile?

public T Resolve<T>() { if (T is Func<X>) return (T) () => Resolve(typeof(X)); return (T)Resolve(typeof(T)); }

Or to put my question another way, if I have a type T, how can I detect if it is an instance of Func<X>, and if so, what is the type of X?

Community · Accepted Answer · 2017-05-23 12:01:25Z

3

take a look at this question from this morning - might give you a good start - C# generic list <T> how to get the type of T?

edited May 23, 2017 at 12:01

CommunityBot

11 silver badge

answered Jun 25, 2009 at 22:01

Scott Ivey

41.7k21 gold badges85 silver badges118 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Marc Gravell Over a year ago

Indeed, replace List with Func and you're done...

Mark Heath Over a year ago

yes, looks like this will do it for me. thanks Now I have a problem that the compiler won't let me cast from () => Resolve(theArgumentType) back to the original T (even if I try to cast to object first). "Cannot convert lambda expression to type 'T' because it is not a delegate type"

SLaks · Accepted Answer · 2009-06-26 12:19:54Z

I misunderstood your question.

It is impossible to do it in one function the way you're trying to because the compiler must have a delegate type to create the lambda as at compile time.

However, this should work.

public T Resolve<T>() { return (T)Resolve(typeof(T)); } public Func<T> LazyResolve<T>() { return () => Resolve<T>(); }

ok I think I understand why its not possible. Shame, because it would be a nice feature for an IoC container.

SLaks · Accepted Answer · 2009-06-25 22:21:13Z

0

In answer to the question in the comment, you need to invoke the lambda expression, not cast it.

answered Jun 25, 2009 at 22:21

SLaks

891k182 gold badges1.9k silver badges2k bronze badges

3 Comments

Mark Heath Over a year ago

I don't want to invoke it yet, I want to pass the Func itself back so that the caller can invoke it when they are ready to

SLaks Over a year ago

Then you need to cast it to Func<T>.

SLaks Over a year ago

I misunderstood; see second answer.

Collectives™ on Stack Overflow

How to detect if a type is a Func<T> and get the type of the T [duplicate]

3 Answers 3

2 Comments

1 Comment

3 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

3 Comments

Linked

Related