How to Handle Circular Dependencies with Dependency Injection in .NET 7 Web API?
I'm collaborating on a project where I'm working on a .NET 7 Web API project where I've set up Dependency Injection (DI) using Microsoft.Extensions.DependencyInjection. Recently, I encountered a circular dependency scenario between two services, `UserService` and `EmailService`. The `UserService` depends on `EmailService` to send notifications when a new user is created, while `EmailService` needs access to `UserService` for certain user-related configurations. When I run the application, I receive an `InvalidOperationException` stating, "want to provide a value for property 'UserService' on type 'EmailService' because it is not a service of the type 'UserService' and is not registered in the service collection." I've tried using `IServiceProvider` to resolve dependencies within the constructors, but it results in a `StackOverflowException`. Here’s a simplified version of my `Startup.cs` configuration: ```csharp public void ConfigureServices(IServiceCollection services) { services.AddTransient<UserService>(); services.AddTransient<EmailService>(); // Other service registrations } ``` And here are the relevant parts of my services: ```csharp public class UserService { private readonly EmailService _emailService; public UserService(EmailService emailService) { _emailService = emailService; } public void CreateUser(User user) { // Logic to create user _emailService.SendWelcomeEmail(user); } } public class EmailService { private readonly UserService _userService; public EmailService(UserService userService) { _userService = userService; } public void SendWelcomeEmail(User user) { // Logic to send email } } ``` I've considered using a factory pattern or breaking the dependencies, but I'm not sure how to implement that cleanly without introducing unnecessary complexity. Any suggestions on how to resolve this circular dependency scenario effectively while adhering to best practices? I recently upgraded to C# stable.