How to add items to a collection while consuming it?

Question

The example below throws an InvalidOperationException, \"Collection was modified; enumeration operation may not execute.\" when executing the code.

var urls         


        

Answer 1

You can probably also create a recursive function, like this (untested):

IEnumerable GetUrl(string url)
{
  foreach(string u in GetUrl(url))
    yield return u;
  foreach(string ret_url in WHERE_I_GET_MY_URLS)
    yield return ret_url;
}

List MyEnumerateFunction()
{
  return new List(GetUrl("http://www.google.com"));
}

In this case, you will not have to create two lists, since GetUrl does all the work.

But I may have missed the point of you program.