Exception during iteration on collection and remove items from that collection [duplicate]

Answer 1

You can iterate over a copy of the collection:

foreach(var fullFilePath in new ArrayList(attachmentsFilePath))
{
    // do stuff
}

Answer 2

do the following:

foreach (var fullFilePath in new List(attachmentsFilePath))
{

this way you create a copy of the original list to iterate through

Answer 3

You could loop over the collection to see which items need to be delete and store those indexes in a separate collection. Finally you would need to loop over the indexes to be deleted in reverse order and remove each from the original collection.

list<int> itemsToDelete

for(int i = 0; i < items.Count; i++)
{
    if(shouldBeDeleted(items[i]))
    {
        itemsToDelete.Add(i);
    }
}

foreach(int index in itemsToDelete.Reverse())
{
    items.RemoveAt(i);
}

Answer 4

    List<string> names = new List<string>() { "Jon", "Eric", "Me", "AnotherOne" };
    List<string> list = new List<string>() { "Person1", "Paerson2","Eric"};

    list.RemoveAll(x => !names.Any(y => y == x));
    list.ForEach(Console.WriteLine);

Answer 5

while enumerating (or using foreach) you cannot modify that collection. If you really want to remove items, then you can mark them and later remove them from list using its Remove method

Answer 6

Another way of doing it, start from the end and delete the ones you want:

List<int> numbers = new int[] { 1, 2, 3, 4, 5, 6 }.ToList();
for (int i = numbers.Count - 1; i >= 0; i--)
{
    numbers.RemoveAt(i);
}