IEnumerableT> is used to pass a single item.

Problem

Is there a standard way of passing a single T item to a method that expects an IEnumerableT> parameter? C# is the programming language, and the framework is version 2.0.

I’m currently using a helper method (it’s.Net 2.0, so I have a slew of casting/projecting helper methods akin to LINQ), but this sounds ridiculous:

public static class IEnumerableExt
{
    // usage: IEnumerableExt.FromSingleItem(someObject);
    public static IEnumerable<T> FromSingleItem<T>(T item)
    {
        yield return item; 
    }
}

Creating and populating a ListT> or an Array and passing it instead of IEnumerableT> is another option.

[Edit] It could be named as an extension method:

public static class IEnumerableExt
{
    // usage: someObject.SingleItemAsEnumerable();
    public static IEnumerable<T> SingleItemAsEnumerable<T>(this T item)
    {
        yield return item; 
    }
}

Is there something I’m overlooking?

[Edit2] We decided that someObject.Yield() (as proposed by @Peter in the comments below) was the best name for this extension method, primarily because of its brevity, so here it is, along with the XML remark if anyone needs it:

public static class IEnumerableExt
{
    /// <summary>
    /// Wraps this object instance into an IEnumerable&lt;T&gt;
    /// consisting of a single item.
    /// </summary>
    /// <typeparam name="T"> Type of the object. </typeparam>
    /// <param name="item"> The instance that will be wrapped. </param>
    /// <returns> An IEnumerable&lt;T&gt; consisting of a single item. </returns>
    public static IEnumerable<T> Yield<T>(this T item)
    {
        yield return item;
    }
}

Asked by Groo

Solution #1

If the method expects an IEnumerable, you must pass anything that is a list, even if it just has one entry.

passing

new[] { item }

I believe the argument should enough.

Answered by Mario F

Solution #2

You can use the System in C# 3.0. Linq. Class that can be enumerated:

// using System.Linq

Enumerable.Repeat(item, 1);

This will generate a new IEnumerable with just your item in it.

Answered by luksan

Solution #3

Your helper method is, in my opinion, the clearest way to go about it. If you pass in a list or an array, an untrustworthy piece of code could cast it and change its contents, resulting in strange behavior in some cases. You could use a read-only collection, but it will very certainly result in even more wrapping. Your solution is as good as it gets in my opinion.

Answered by Jon Skeet

Solution #4

You can construct a generic extension method in C# 3 (I know you said 2) to make the syntax a little more acceptable:

static class IEnumerableExtensions
{
    public static IEnumerable<T> ToEnumerable<T>(this T item)
    {
        yield return item;
    }
}

The item is then the client code. ToEnumerable().

Answered by Ðаn

Solution #5

This helper method can be used for a single item or a group of items.

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

Answered by duraid

Post is based on https://stackoverflow.com/questions/1577822/passing-a-single-item-as-ienumerablet