Anonymous types should implement the interface they are assigned to

[AArnott]

It's almost like duck-typing, but still strongly typed. When I create an anonymous type that the C# compiler can see must implement a particular interface in order to compile, the generated anonymous type should implement that interface implicitly.

For example, this should compile:

public interface IDiffBaseInfo
{
    string Id { get; set; }
    string Description { get; set; }
}

public IDiffBaseInfo GetCommit()
{
    return new { Id = "a", Description = "b" };
}

[HaloFour]

Anonymous types in C# are readonly.

I could possibly see this working if the properties were declared as readonly also, but I'd prefer a more explicit syntax for creating the anonymous type, e.g. new IDiffBaseInfo { ... } like Java anonymous classes.

[bondsbw]

Similar: #100

[AArnott]

#100 seems to be dealing with omitting the type in a new expression where the type is defined elsewhere. It doesn't deal with anonymous types.

[Joe4evr]

dotnet/roslyn#13 (comment)

[AArnott]

Ah ya, that looks like a superset of what I'm asking for here. I'm certainly not asking to implement interfaces with methods on them. But the response to it doesn't bode well for this smaller) request.

[bondsbw]

@AArnott Right, but #100 gives the caller a similar syntax to work with. It is still more work on the definition side.

[glucaci]

It's still something happening with this? @AArnott @gafter

In #100 you should provide an implementation to can use the new keyword in that way.

I find this construct new IFoo { Bar = "Foo" } very useful for tests.

[jnm2]

@glucaci You are asking for dotnet/roslyn#13 (comment):

We have no expectation of ever doing anything like this.

[glucaci]

@jnm2 yes, thanks for pointing that.
I saw that the dotnet/roslyn#13 feature request was closed without any sustainable explanation.

[glucaci]

Following @MadsTorgersen dotnet/roslyn#13 (comment)

You could certainly imagine an evolution of anonymous objects in C# that would combine the current behavior with the ability to inherit classes, implement interfaces and supply member implementations.

maybe we can have a more recent update about what he is thinking on this topic.

Pointing to local classes (dotnet/roslyn#13 (comment)) has nothing to do with this request because than is useless, I can declare a class anywhere else and use it.
The idea is to not implement that interface at all and still be able to construct objects.

[gafter]

maybe we can have a more recent update about what he is thinking on this topic.

I suspect it is unlikely he has thought about it since then.