Concatenate multiple IEnumerable

Question

I\'m trying to implement a method to concatenate multiple Lists e.g.

List l1 = new List { \"1\", \"2\" };
List

        

Answer 1

Just for completeness another imo noteworthy approach:

public static IEnumerable<T> Concatenate<T>(params IEnumerable<T>[] List)
{
    foreach (IEnumerable<T> element in List)
    {
        foreach (T subelement in element)
        {
            yield return subelement;
        }
    }
}

Answer 2

All you have to do is to change:

public static IEnumerable<T> Concatenate<T>(params IEnumerable<T> lists)

to

public static IEnumerable<T> Concatenate<T>(params IEnumerable<T>[] lists)

Note the extra [].

Answer 3

If you want to make your function work you need an array of IEnumerable:

public static IEnumerable<T> Concartenate<T>(params IEnumerable<T>[] List)
{
    var Temp = List.First();
    for (int i = 1; i < List.Count(); i++)
    {
        Temp = Enumerable.Concat(Temp, List.ElementAt(i));
    }
    return Temp;
}

Answer 4

Use SelectMany:

public static IEnumerable<T> Concatenate<T>(params IEnumerable<T>[] lists)
{
    return lists.SelectMany(x => x);
}