Shortcut for creating single item list in C#

Question

In C#, is there an inline shortcut to instantiate a List with only one item.

I\'m currently doing:

new List( new string[] { \"         


        

Answer 1

Yet another way, found on "C#/.Net Little wonders" (unfortunately, the site doesn't exist anymore):

Enumerable.Repeat("value",1).ToList()

Answer 2

I would just do

var list = new List<string> { "hello" };

Answer 3

var list = new List<string>(1) { "hello" };

Very similar to what others have posted, except that it makes sure to only allocate space for the single item initially.

Of course, if you know you'll be adding a bunch of stuff later it may not be a good idea, but still worth mentioning once.

Answer 4

For a single item enumerable in java it would be Collections.singleton("string");

In c# this is going to be more efficient than a new List:

public class SingleEnumerator<T> : IEnumerable<T>
{
    private readonly T m_Value;

    public SingleEnumerator(T value)
    {
        m_Value = value;
    }

    public IEnumerator<T> GetEnumerator()
    {
        yield return m_Value;
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        yield return m_Value;
    }
}

but is there a simpler way using the framework?

Answer 5

Michael's idea of using extension methods leads to something even simpler:

public static List<T> InList<T>(this T item)
{
    return new List<T> { item };
}

So you could do this:

List<string> foo = "Hello".InList();

I'm not sure whether I like it or not, mind you...

Answer 6

I've got this little function:

public static class CoreUtil
{    
    public static IEnumerable<T> ToEnumerable<T>(params T[] items)
    {
        return items;
    }
}

Since it doesn't prescribe a concrete return type this is so generic that I use it all over the place. Your code would look like

CoreUtil.ToEnumerable("title").ToList();

But of course it also allows

CoreUtil.ToEnumerable("title1", "title2", "title3").ToArray();

I often use it in when I have to append/prepend one item to the output of a LINQ statement. For instance to add a blank item to a selection list:

CoreUtil.ToEnumerable("").Concat(context.TrialTypes.Select(t => t.Name))

Saves a few ToList() and Add statements.

(Late answer, but I stumbled upon this oldie and thought this could be helpful)