How can I create a singleton IEnumerable?

问题

Does C# offer some nice method to cast a single entity of type T to IEnumerable<T>?

The only way I can think of is something like:

T entity = new T();
IEnumerable<T> = new List { entity }.AsEnumerable();

And I guess there should be a better way.

回答1:

Your call to AsEnumerable() is unnecessary. AsEnumerable is usually used in cases where the target object implements IQueryable<T> but you want to force it to use LINQ-to-Objects (when doing client-side filtering on a LINQ-compatible ORM, for example). Since List<T> implements IEnumerable<T> but not IQueryable<T>, there's no need for it.

Anyway, you could also create a single-element array with your item;

IEnumerable<T> enumerable = new[] { t };

Or Enumerable.Repeat

IEnumerable<T> enumerable = Enumerable.Repeat(t, 1);

回答2:

I use

Enumerable.Repeat(entity, 1);

回答3:

var entity = new T();
var singleton = Enumerable.Repeat(entity, 1);

(Although I'd probably just do var singleton = new[] { entity }; in most situations, especially if it was only for private use.)

来源：https://stackoverflow.com/questions/4960091/how-can-i-create-a-singleton-ienumerable