advanced patterns When Using LINQ's GroupBy with Complex Objects in C#
After trying multiple solutions online, I still can't figure this out. I'm working with an scenario with LINQ's `GroupBy` method when trying to group a list of complex objects. I have a list of `Order` objects, each containing an `Id`, `CustomerId`, and a `TotalAmount`. I want to group these orders by `CustomerId` and calculate the total amount for each customer. However, I'm getting unexpected results where some customers seem to be missing from the grouped result. Here's what I have: ```csharp public class Order { public int Id { get; set; } public int CustomerId { get; set; } public decimal TotalAmount { get; set; } } var orders = new List<Order> { new Order { Id = 1, CustomerId = 1, TotalAmount = 100 }, new Order { Id = 2, CustomerId = 2, TotalAmount = 200 }, new Order { Id = 3, CustomerId = 1, TotalAmount = 150 }, new Order { Id = 4, CustomerId = 3, TotalAmount = 300 }, }; var groupedOrders = orders.GroupBy(o => o.CustomerId) .Select(g => new { CustomerId = g.Key, TotalSpent = g.Sum(o => o.TotalAmount) }).ToList(); ``` When I run this code, `groupedOrders` returns only two entries instead of three, which means one customer is missing. I checked the input list and all `CustomerId` values are indeed unique as per the orders I have. I am using .NET 5.0, and the LINQ queries are running fine otherwise. I suspect this might be related to how I'm initializing or using the `Order` class, but I need to see any obvious issues. I also tried debugging and inspecting the original list before grouping, and all entries look correct. Is there a specific reason why a `GroupBy` might ignore some entries? Any help with this would be greatly appreciated! I'm working on a API that needs to handle this. Am I missing something obvious?