Adding an element during enumeration

Question

When the first condition doesn't satisfy because product is not already in the collection, it's then added via the else statement. However, when it is added - the foreach loop continues until all objects have been iterated - yet it never enters p._id == product._id and will continue to the else statement, adding another identical object.

May this be because I'm adding an element to a collection during enumeration? It's not actually added until enumeration is completed.

public void AddProduct(Product product)
{
    foreach(Product p in products)
    {
        if(p._id == product._id)
        {
            product._qty = product._qty + p._qty;
        }
        else
        {
            inventory.Add(p);
        }
    }
}

Answer 1

使用While循环或for循环，它不会抛出CollectionChangedException。