What's the Best Way to Add One Item to an IEnumerable?

Question

Here\'s how I would add one item to an IEnumerable object:

//Some IEnumerable object
IEnumerable arr = new string[] { \"ABC\", \"DEF\"         


        

Answer 1

Write an extension method ConcatSingle :)

public static IEnumerable ConcatSingle(this IEnumerable source, T item)
{
    return source.Concat(new [] { item } );
}

But you need to be more careful with your terminology.
You can't add an item to an IEnumerable. Concat creates a new instance.

Example:

var items = Enumerable.Range(1, 10)
Console.WriteLine(items.Count()); // 10
var original= items;
items = items.ConcatSingle(11);
Console.WriteLine(original.Count());   // 10
Console.WriteLine(items.Count()); // 11

As you can see, the original enumeration - which we saved in original didn't change.