连接多个IEnumerable <T>

Question

我正在尝试实现一个连接多个Lists 的方法

List<string> l1 = new List<string> { "1", "2" };
List<string> l2 = new List<string> { "1", "2" };
List<string> l3 = new List<string> { "1", "2" };
var result = Concatenate(l1, l2, l3);

但我的方法不起作用:

public static IEnumerable<T> Concatenate<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 1

用途SelectMany:

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

Answer 2

为了完整起见，另一种值得注意的方法：

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