Issues with LINQ Distinct on Complex Object List in C# - Unexpected Results
I'm not sure how to approach Quick question that's been bugging me - I've searched everywhere and can't find a clear answer... I'm currently facing an issue when trying to use LINQ's `Distinct` method on a list of complex objects in C#. The objects in question are instances of a `Product` class which looks like this: ```csharp public class Product { public int Id { get; set; } public string Name { get; set; } public decimal Price { get; set; } public string Category { get; set; } } ``` I have a list of `Product` objects that I want to filter for unique products based on their `Id` property. My current approach is as follows: ```csharp var products = new List<Product> { new Product { Id = 1, Name = "Apple", Price = 0.5m, Category = "Fruits" }, new Product { Id = 1, Name = "Apple", Price = 0.5m, Category = "Fruits" }, new Product { Id = 2, Name = "Banana", Price = 0.3m, Category = "Fruits" }, }; var distinctProducts = products.Distinct().ToList(); ``` However, when I execute this code, the `distinctProducts` list still contains two entries for the Apple product (with Id 1) instead of just one. I suspect that it might be due to the fact that `Distinct` uses the default equality comparer, which compares object references rather than the properties of the `Product` class. To resolve this, I've tried implementing `IEqualityComparer<Product>` like this: ```csharp public class ProductComparer : IEqualityComparer<Product> { public bool Equals(Product x, Product y) { return x.Id == y.Id; } public int GetHashCode(Product obj) { return obj.Id.GetHashCode(); } } ``` And then calling `Distinct` with this comparer: ```csharp var distinctProducts = products.Distinct(new ProductComparer()).ToList(); ``` This approach seems to work correctly, but Iām concerned about the performance implications of using a custom comparer, especially if the product list grows large. Is there a more efficient way to achieve distinct filtering or any best practices regarding this scenario? Also, could there be any circumstances where using `Distinct` this way might still lead to unexpected behavior? Iām using .NET 5.0 for this project, and I would appreciate any insights on this topic. This is part of a larger API I'm building. Is there a better approach? I'm working on a service that needs to handle this. Am I missing something obvious? I'm using C# latest in this project. This is part of a larger desktop app I'm building. Could this be a known issue?