CODEWITHSUNDEEP
c#linqc#-3.0
Marcel Lamothe
Marcel Lamothe

Reputation: 12912

Favorite way to create an new IEnumerable<T> sequence from a single value?

I usually create a sequence from a single value using array syntax, like this:

IEnumerable<string> sequence = new string[] { "abc" };

Or using a new List. I'd like to hear if anyone has a more expressive way to do the same thing.

Upvotes: 108

Views: 98442

Answers (4)

JaredPar
JaredPar

Reputation: 755259

Your example is not an empty sequence, it's a sequence with one element. To create an empty sequence of strings you can do

var sequence = Enumerable.Empty<string>();

EDIT OP clarified they were looking to create a single value. In that case

var sequence = Enumerable.Repeat("abc", 1);

Upvotes: 154

Andrew
Andrew

Reputation: 354

or just create a method

public static IEnumerable<T> CreateEnumerable<T>(params T[] items)
{
    if(items == null)
        yield break;

    foreach (T mitem in items)
        yield return mitem;
}

or

public static IEnumerable<T> CreateEnumerable<T>(params T[] items)
{
   return items ?? Enumerable.Empty<T>();
}

usage : 

IEnumerable<string> items = CreateEnumerable("single");

Upvotes: 8

nawfal
nawfal

Reputation: 73253

Or even shorter,

string[] single = { "abc" };

I would make an extension method: 

public static T[] Yield<T>(this T item)
{
    T[] single = { item };
    return single;
}

Or even better and shorter, just 

public static IEnumerable<T> Yield<T>(this T item)
{
    yield return item;
}

Perhaps this is exactly what Enumerable.Repeat is doing under the hood.

Upvotes: 25

Bryan Watts
Bryan Watts

Reputation: 45465

I like what you suggest, but with the array type omitted:

var sequence = new[] { "abc" };

Upvotes: 79

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