Intelligent way of removing items from a List while enumerating in C#

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The best solution is usually to use the RemoveAll() method:

myList.RemoveAll(x => x.SomeProp == "SomeValue");

Or, if you need certain elements removed:

MyListType[] elems = new[] { elem1, elem2 };
myList.RemoveAll(x => elems.Contains(x));

This assume that your loop is solely intended for removal purposes, of course. If you do need to additional processing, then the best method is usually to use a for or while loop, since then you’re not using an enumerator:

for (int i = myList.Count - 1; i >= 0; i--)
{
    // Do processing here, then...
    if (shouldRemoveCondition)
    {
        myList.RemoveAt(i);
    }
}

Going backwards ensures that you don’t skip any elements.

Response to Edit:

If you’re going to have seemingly arbitrary elements removed, the easiest method might be to just keep track of the elements you want to remove, and then remove them all at once after. Something like this:

List<int> toRemove = new List<int>();
foreach (var elem in myList)
{
    // Do some stuff

    // Check for removal
    if (needToRemoveAnElement)
    {
        toRemove.Add(elem);
    }
}

// Remove everything here
myList.RemoveAll(x => toRemove.Contains(x));

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