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

I assume you want to iterate over the whole list, and each item you add to it? If so I would suggest recursion:

var urls = new List();
var turls = new List u)
{
    foreach(string url in u)
    {
        List newUrls = GetLinks(url);

        urls.AddRange(newUrls);

        iterate(newUrls);
    }
}