Defining a type with a property that is an interface

Question

I am looking for functional equivalence for the following C# code:

public virtual ICollection<Dog> Dogs { get; set; }

I have been up and down SO and MSDN, to no avail. Is there a different construct for properties other than this:

let mutable dogID = 0

member public self.DogID
    with get() = dogID
    and set(value) = dogID <- value

What would you expect the initial value to be? Your sample code is fine, you just need to use an `ICollection` rather than `0` (which is an `Int`) for the initializer. — Ganesh Sittampalam, Aug 10 '14 at 19:17
I don't know what the initial value will be be. It will just implement ICollection. — Jamie Dixon, Aug 10 '14 at 19:20
If someone creates an instance of your class and retrieves the `Dogs` property before setting it, what value should they get? — Ganesh Sittampalam, Aug 10 '14 at 19:34

score 3 · Answer 1 · answered Aug 10 '14 at 19:17

3

You can use auto properties:

member val Dogs = List<Dog>() with get,set

answered Aug 10 '14 at 19:17

7sharp9

But not a List, I need a ICollection. Compiler says "Invalid use of an interface type" when I replace List with ICollection – Jamie Dixon Aug 10 '14 at 19:19
3

Add a cast to be explicit: :> ICollection – 7sharp9 Aug 10 '14 at 19:20
I mainly use auto properties like this when implementing a C# defined interface. – 7sharp9 Aug 10 '14 at 19:51

score 2 · Answer 2 · edited May 23 '17 at 12:05

2

OK, Apparently I need to SO (the verb) even better. I found this this which led me to this:

let mutable dogs = List<DOG>() :> ICollection<DOG> 


member public self.Dogs
    with get() = dogs
    and set(value) = dogs <- value

Thanks to Dave for pointing me at the explicit class. Also, Genesh, I think that is what your question was? Thanks for helping also.

edited May 23 '17 at 12:05

Community

answered Aug 10 '14 at 19:38

Jamie Dixon

3

That's not going to make the property `virtual`, if that's important to you. The documentation explains how to do that: http://msdn.microsoft.com/en-us/library/dd483467.aspx – Mark Seemann Aug 10 '14 at 20:23
You didn't ask but I'd also strongly consider whether or not that collection needs to be mutable. Mutable is a code smell in functional programming--not necessarily wrong but something to really think about. You're more likely to want to create a new object if you need to associate a different dog collection with it. – Onorio Catenacci Aug 12 '14 at 21:19
I am mapping back to an interfaces that was defined in C#. LOL, the collection is from Entity Frameworks – Jamie Dixon Aug 12 '14 at 23:25

2 Answers2