Question

I have a loop that iterates through elements in a list. I am required to remove elements from this list within the loop based on certain conditions. When I try to do this in C#, I get an exception. apparently, it is not allowed to remove elements from the list which is being iterated through. The problem was observed with a foreach loop. Is there any standard way to get around this problem?

Note : One solution I could think of is to create a copy of the list solely for iteration purpose and to remove elements from the original list within the loop. I am looking for a better way of dealing with this.

Answer 1

When using List<T> the ToArray() method helps in this scenario vastly:

List<MyClass> items = new List<MyClass>();
foreach (MyClass item in items.ToArray())
{
    if (/* condition */) items.Remove(item);
}

The alternative is to use a for loop instead of a foreach, but then you have to decrement the index variable whenever you remove an element i.e.

List<MyClass> items = new List<MyClass>();
for (int i = 0; i < items.Count; i++)
{
    if (/* condition */)
    {
        items.RemoveAt(i);
        i--;
    }
}