c# - List<T>.AddRange and the yield statement -

i aware yield keyword indicates method in appears iterator. wondering how works list<t>.addrange.

let's use below example:

static void main() {     foreach (int in myints())     {         console.write(i);     } }  public static ienumerable<int> myints() {       (int = 0; < 255; i++)     {         yield return i;     } } 

so in above example after each yield, value returned in foreach loop in main , printed console.

if change main this:

static void main() {     var mylist = new list<int>();     mylist.addrange(myints()); } 

how work? addrange called each int returned yield statement or somehow wait 255 values before adding entire range?

the implementation of addrange iterate on ienumerable input using iterator's .movenext() method until values have been produced yielding method. can seen here.

so mylist.addrange(myints()); called once , implementation forces myints return of values before moving on.

addrange exhausts values of iterator because of how implemented, following hypothetic method evaluate first value of iterator:

public void addfirst<t>(ienumerable<t> collection) {     insert(collection.first()); } 

an interesting experiment while play around add console.writeline(i); line in myints method see when each number generated.