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

You can also do

new List<string>() { "string here" };

Answer 2

Simply use this:

List<string> list = new List<string>() { "single value" };

You can even omit the () braces:

List<string> list = new List<string> { "single value" };

Update: of course this also works for more than one entry:

List<string> list = new List<string> { "value1", "value2", ... };

Answer 3

A different answer to my earlier one, based on exposure to the Google Java Collections:

public static class Lists
{
    public static List<T> Of<T>(T item)
    {
        return new List<T> { item };
    }
}

Then:

List<string> x = Lists.Of("Hello");

I advise checking out the GJC - it's got lots of interesting stuff in. (Personally I'd ignore the "alpha" tag - it's only the open source version which is "alpha" and it's based on a very stable and heavily used internal API.)

Answer 4

Inspired by the other answers (and so I can pick it up whenever I need it!), but with naming/style aligned with F# (which has a standard singleton function per data structure*):

namespace System.Collections.Generic
{
    public static class List
    {
        public static List<T> Singleton<T>(T value) => new List<T>(1) { value };
    }
}

* except for ResizeArray itself of course, hence this question :)

---

In practice I actually name it Create to align with other helpers I define such as Tuple.Create, Lazy.Create[2], LazyTask.Create etc:

namespace System.Collections.Generic
{
    public static class List
    {
        public static List<T> Create<T>(T value) => new List<T>(1) { value };
    }
}

[2]

namespace System
{
    public static class Lazy
    {
        public static Lazy<T> Create<T>(Func<T> factory) => new Lazy<T>(factory);
    }
}

Answer 5

new[] { "item" }.ToList();

It's shorter than

new List<string> { "item" };

and you don't have to specify the type.

Answer 6

Use an extension method with method chaining.

public static List<T> WithItems(this List<T> list, params T[] items)
{
    list.AddRange(items);
    return list;
}

This would let you do this:

List<string> strings = new List<string>().WithItems("Yes");

or

List<string> strings = new List<string>().WithItems("Yes", "No", "Maybe So");

Update

You can now use list initializers:

var strings = new List<string> { "This", "That", "The Other" };

See http://msdn.microsoft.com/en-us/library/bb384062(v=vs.90).aspx