c# - Why can I use a collection initializer with private set access from another class?

Question

Consider the following code:

public sealed class Order
{
    public Order()
    {
        Items = new List<OrderItem>();
    }

    public List<OrderItem> Items { get; private set; }
}

public sealed class OrderItem
{
}

and here's Order initialization in another class.

var order = new Order
{
    Items =
    {
        new OrderItem(),
        new OrderItem()
    }
};

Could you explain why it works? As you see the Order has private set property, so I thought it would be impossible to set its value.

Answer 1

Your statement works because the collection initialization syntax uses the Add() method to add the items to the collection rather than setting the member to a new instance of a collection. Essentially, your code is the equivalent of:

var order = new Order();
order.Items.Add(new OrderItem());
order.Items.Add(new OrderItem());

Which is fine since you only ever use the getter method.