Icollection property in class is not instantiated

Question

I have the product class and in that class I have this property

public virtual ICollection<CspProduct> CspItems { get; set; } 

Here we take the products

var products = _productService.GetAll().ToList();

and here the items

var items = _orderService.GetItemsFromOrder(_order).Where(x => x.CurrencyCode == 23).ToList();

I did the Join below

var result = products.Join(
                items,
                p => p.Id,
                i => i.ProductId,
                (p, i) => new { produtos = p, itens = i }) 
                .Where(x => x.produtos.Hidden == false && x.itens.CurrencyCode == 23)
                .Select(x => new SubscriptionProductModel
                {
                    Name = x.produtos.Name,
                    Partnumber = x.produtos.PartNumber,
                    Markup = 0M,
                    OfferUri = x.produtos.CspItems.Select(s => new { s.OfferUri}).FirstOrDefault().ToString(),
                    Dollar = x.itens.BasePriceUSD,
                    Real = x.itens.BasePriceBRL
                }).ToList();

It turns out that when I get on that line inside the Join

OfferUri = x.produtos.CspItems.Select(s => new { s.OfferUri}).FirstOrDefault().ToString()

Makes a mistake of:

Undefined object reference for an object instance

How do I instantiate an object inside another when I’m running a lambda?

Answer 1

It may be that the Firstordefault function is returning null because the Cspitems list is empty, or that the variable s of the lambda expression is null. If you want the Offeruri variable to be met even with these conditions use the following code:

OfferUri = x.produtos.CspItems.Select(s => new { s?.OfferUri }).FirstOrDefault()?.ToString()

But I think if your intention is to take the value in s.Offeruri should be like this:

OfferUri = x.produtos.CspItems.FirstOrDefault(s => s?.OfferUri )