removing items from a generic List<t>

Question

I have the following method, I wish to remove items from my collection that match the product Id. Seems fairly straight forward, but i get an exception. Basically my collection is getting out of sync. So what is the best way to remove an item from a collection.

public void RemoveOrderItem(Model.Order currentOrder, int productId)
{

    foreach (var orderItem in currentOrder.OrderItems)
    {
        if (orderItem.Product.Id == productId)
        {
            currentOrder.OrderItems.Remove(orderItem);
        }
    }
}

Exception Details: System.InvalidOperationException: Collection was modified; enumeration operation may not execute

Answer 1

Modifying a collection inside a loop doesn’t work. To work around that, List has a few methods that allow “batch” modifications of a collection. In your case, use:

currentOrder.OrderItems.RemoveAll(x => x.Product.Id == productId)

Answer 2

You can't modify a collection while iterating it. Just use a normal for loop instead of a foreach loop.

Answer 3

By looping this way you can not remove items because its in collection it keeps the track of the stored items.

Easy way to do this :

   authorsList.RemoveAll(x => x.ProductId == productId);

or

   authorsList = authorsList.Where(x => x.ProductId!= productId).ToList();

Answer 4

You can't remove an item from a collection you are iterating through, you could keep track of the orderItem, then remove it after you finish looping