C# preventing Collection Was Modified exception

Question

Does

 foreach(T value in new List(oldList) )

is dangerous (costly) when oldList contains 1 millions of object T ?

More g

Answer 1

If you are using Foreach loop for modifying collection then you will get this error as below.

List li = new List();
    li.Add("bhanu");
    li.Add("test");

    foreach (string s in li)
    {
        li.Remove(s);
    }

Solution - use For Loop as below.

for (int i = 0; i < li.Count; i++)
    {
        li.RemoveAt(i);
        i--;
    }