嵌套泛型类型的扩展方法

Question

I'm writing an extension method, that should work on a generic of generics, say IEnumerable<IEnumerable<T>> - for example

public static IEnumerable<T> SelectAll<T>(this IEnumerable<IEnumerable<T>> source)
{
    return source.SelectMany(x => x);
}

Now, how do I make it accept a parameter that's actually a List<List<T> ? I've only been able to make it swallow a List<IEnumerable<T>> , is there a way without manually casting to that?

Answer 1

It's working nicely, what's the problem you're having?

var w = new List<List<int>>(){
    new List<int>{2,3,4},
    new List<int>{5,3,2}
};

w.SelectAll().Dump();