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

just like this

var itemsToBeRemoved = new List();

foreach (T item in myHugeList) 
{
    if (/**/)
         itemsToBeRemoved.Add(item);
}

myHugeList.RemoveRange(itemsToBeRemoved);