Linq投影计数（按ID）

Question

我是Linq Projection的新手。 我只想知道如何按ID计数。 我需要计算每个客户的订单和平均订单价格。

public IQueryable<TemporaryCustomerModel> GetCustomersWithOrdersCountAndAveragePrice()
    {
        var result = dataContext.Customers
        .Include(u => u.Order)
        .Select(r => new TemporaryCustomerModel()
        {
            Id = r.Id,
            FullName = r.Name + ' ' + r.Surname,
            Email = r.Email,
            Birthdate = r.Birthdate,
            Gender = r.Gender.GetName(),
            Orders = ???, //Count orders for every customer
            AvgPrice = ??? //Average order price
        });

        return result;
    }

Answer 1

假设您的Customer类包含List<Order> Orders ，而Order类包含字段Price

...
Orders = r.Orders.Count(),
AvgPrice = r.Orders.Average(o => o.Price)
...