Chaining IEnumerables in C#?

Question

Is there a simple built-in way to take an ordered list of IEnumerables and return a single IEnumerable which yields, in order, all the elements in the first, then the second, and so on.

I could certainly write my own, but I wanted to know whether there was already a way to accomplish this seemingly useful task before I do it.

Answer 1

Try SelectMany.

IEnumerable<int> Collapse(IEnumerable<IEnumerable<int>> e){
 return e.SelectMany(x => x );
}

The purpose of this function is to flatten a group of IEnumerable<IEnumerable<T>> into an IEnumerable<T>. The returned data will preserve the original order.

Answer 2

Further to JaredPar's (correct) answer - also query syntax:

var all = from inner in outer
          from item in inner
          select item;