C # Extension Method for AddItem for IEnumerable <T>

Question

What is the best way to add an item to an IEnumerable collection using the extension method?

Answer 1

enumerable.Concat(new[]{ objToAdd }) 

Answer 2

You cannot (directly). The purpose of the interface is to display a counter.

Change You will need to convert IEnumerable to another type (e.g. List ) or concatenation to add, which will not add the existing IEnumerable , but concatenate instead of IEnumerable instead.

The only option is to check if it implements any interfaces that you can use to add as IList, ICollection, IDictionary, ILookup, ... and even then you will not be sure that you can add IEnumerable to the existing one.

Answer 3

I have this in my IEnumerableExtensions class, but I'm not sure if it is too efficient, but I use it very sparingly.

 public static IEnumerable<T> Add<T>(this IEnumerable<T> enumerable, T item) { var list = enumerable.ToList(); list.Add(item); return list; }