Adding items in order gives NullReferenceException (WooCommerce, in C# and using WooCommerce.NET addin.

I am trying to use this code for making an order in Woocommerce, using this add-on :https://github.com/XiaoFaye/WooCommerce.NET. My code is this:

var order = new Order() { status = "pending" };
order.currency = "EUR";
order.line_items.Add(new OrderLineItem()
{
id=44,
product_id = 44,
quantity=2
}
);
order.customer_id = 1;

Task ord = wc.Order.Add(order);
ord.Wait();
But everytime it gives me this exception:
System.NullReferenceException: 'Object reference not set to an instance of an object.'

I have tried everything but no success...

pink glitterAsked: 2018-09-26

Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

Experts Exchange Solution brought to you by

Enjoy your complimentary solution view.

Get every solution instantly with Premium. Start your 7-day free trial.

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

LVL 50

Chris StanyonWebDevCommented: 2018-09-26

You haven't said which line gives you the error, so I'm going to guess that it's either line 3 (order.line_items.Add) or 12 (Task ord = wc.Order.Add(order);

Both of these lines look like they're adding an object to list, so it's possible that the list itself hasn't been initialised:

order.line_items = new List<OrderLineItem>();
order.line_items.Add(new OrderLineItem()
   ...

Open in new window

pink glitterAuthor Commented: 2018-09-26

@Chris Stanyon
Hello and thanks for answering! Sorry that i didn't mention it... The line in question is this

order.line_items.Add(new OrderLineItem()
{
id=44,
product_id = 44,
quantity=2
}
);

Thanks again!

LVL 32

Chinmay PatelChief Technical NinjaCommented: 2018-09-26

On which line you get this exception? Is it when you try to add Products?

order.line_items.Add(new OrderLineItem()

Open in new window

Maybe you would want to first initialize line_items?

i.e.

order.line_items = new line_items()

Open in new window

LVL 50

Chris StanyonWebDevCommented: 2018-09-26

Hey Pink Glitter,

Yeah ... that makes sense. Basically, you're trying to add a new OrderLineItem to the line_items property, and that property is null, so you'll need to follow my code example and init that property to a new list before adding items to it.

order.line_items = new List<OrderLineItem>();

Open in new window

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial

LVL 37

it_saigeDeveloperCommented: 2018-09-26

It depends on what your collection type is but, you could do something like this:

var order = new Order { status = "pending" };
order.currency = "EUR";
order.line_items = new List<OrderLineItem>() { new OrderLineItem { id = 44, product_id = 44, quantity = 2 } };
order.customer_id = 1;

Open in new window

-saige-