Trouble with LINQ GroupBy Returning Unexpected Results in C# 10 with EF Core
After trying multiple solutions online, I still can't figure this out. I'm refactoring my project and I've searched everywhere and can't find a clear answer. I'm working with an scenario with using LINQ's `GroupBy` method while querying data from a SQL Server database using Entity Framework Core 6. I expect to group a collection of `Order` objects by `CustomerId` and count the number of orders per customer. However, the results are not as expected, and I see duplicate customer IDs in the output. Here's the code I'm using: ```csharp var groupedOrders = await _context.Orders .GroupBy(o => o.CustomerId) .Select(g => new { CustomerId = g.Key, OrderCount = g.Count() }) .ToListAsync(); ``` When I run this code, I get the following result: ``` CustomerId: 1, OrderCount: 2 CustomerId: 1, OrderCount: 2 CustomerId: 2, OrderCount: 1 CustomerId: 3, OrderCount: 1 ``` The `CustomerId` 1 appears twice, which is not what I expected. I've tried adding `.Distinct()` before the `.Select()`, but that didn't solve the question. I also verified that there are no duplicate records in the `Orders` table itself. I suspect it might be related to how I'm configuring my DbContext or possibly the relationships defined in my models. Here's the relevant part of my `Order` class definition: ```csharp public class Order { public int Id { get; set; } public int CustomerId { get; set; } public DateTime OrderDate { get; set; } // Other properties... } ``` And in my DbContext: ```csharp public class MyDbContext : DbContext { public DbSet<Order> Orders { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<Order>().HasKey(o => o.Id); } } ``` I've double-checked for any subtle issues in my queries, and I've also tried executing the same SQL query directly in SQL Server Management Studio, which yields the correct results. Any insights on why LINQ might be returning unexpected results in this case? My development environment is Ubuntu. What's the best practice here? For context: I'm using C# on Ubuntu. What's the best practice here? This issue appeared after updating to C# LTS. Could someone point me to the right documentation? Any help would be greatly appreciated! For reference, this is a production web app. Is there a simpler solution I'm overlooking? Could someone point me to the right documentation? My development environment is Debian.