How do you create a generically constrained property on an interface?

Question

This is perfectly valid:

public interface IWidgetGetter { IEnumerable<T> GetWidgets<T>() where T : IWidget; }

That is, it defines an untyped interface that includes a method to get a IEnumerable of some type that implements IWidget.

How do I make this into a property?

Things that don't work:

IEnumerable<T> Widgets<T> { get; set; } where T : IWidget IEnumerable<T> Widgets { get; set; } where T : IWidget IEnumerable<T> Widgets where T : IWidget { get; set; } IEnumerable<T> Widgets<T> where T : IWidget { get; set; }

stackoverflow.com/questions/8620883/…

Erti-Chris Eelmaa
– Erti-Chris Eelmaa

2014-12-17 18:45:07 +00:00
Commented Dec 17, 2014 at 18:45 — Erti-Chris Eelmaa
– Erti-Chris Eelmaa, Commented Dec 17, 2014 at 18:45

Lucas Trzesniewski · Accepted Answer · 2014-12-17 18:04:47Z

There is no such thing as a generic property.

A type parameter is still a kind of parameter. Just like you couldn't turn a method that takes an argument into a property, you can't turn a generic method into a property either.

The closest thing you could do is this:

public interface IWidgetGetter<T> where T : IWidget { IEnumerable<T> Widgets { get; } }

Matija Grcic · Accepted Answer · 2014-12-17 18:37:24Z

@Lucas Trzesniewski answered but i would like to add that you can also use a different type parameter TOutput which becomes a generic type parameter instead of using type parameter on the interface definition T.

 public interface MyInterface<T> : IEnumerable<T> { IEnumerable<TOutput> AsEnumerable<TOutput>(); }

Then you can use TypeDescriptor.Converter which knows how to do conversions for primitive types or maybe leverage extension methods it really depends on your case.

public class MyClass<T> : MyInterface<T> { public IEnumerable<TOutput> AsEnumerable<TOutput>() { var converter = TypeDescriptor. GetConverter(typeof(T)); //do what you want foreach(var item in someList) { var result = converter.ConvertTo(item, typeof(TOutput)); yield return (TOutput)result: } } }

Collectives™ on Stack Overflow

How do you create a generically constrained property on an interface?

2 Answers 2

Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Linked

Related