Differences Between Scoped, Transient, And Singleton Service

Introduction

In this article, we will see the difference between AddScoped vs AddTransient vs AddSingleton in .net core.

Why we require

• It defines the lifetime of object creation or a registration in the .net core with the help of Dependency Injection.
• The DI Container has to decide whether to return a new object of the service or consume an existing instance.
• The lifetime of the Service depends on how we instantiate the dependency.
• We define the lifetime when we register the service.

Three types of lifetime and registration options

1. Scoped
2. Transient
3. Singleton

Scoped

• In this service, with every HTTP request, we get a new instance.
• The same instance is provided for the entire scope of that request.
  • eg., if we have a couple of parameter in the controller, both object contains the same instance across the request
• This is a better option when you want to maintain a state within a request.

services.AddScoped<IAuthService,AuthService>();

Transient

• A new service instance is created for each object in the HTTP request.
• This is a good approach for the multithreading approach because both objects are independent of one another.
• The instance is created every time they will use more memory and resources and can have a negative impact on performance
• Utilize for the lightweight service with little or no state.

services.AddTransient<ICronJobService,CronJobService>();

Singleton

• Only one service instance was created throughout the lifetime.
• Reused the same instance in future, wherever the service is required
• Since it's a single lifetime service creation, memory leaks in these services will build up over time.
• Also, it has memory efficient as they are created once reused everywhere.

services.AddSingleton<ILoggingService, LoggingService>();

When to use which Service

Singleton approach => We can use this for logging service, feature flag(to on and off module while deployment), and email service

Scoped approach => This is a better option when you want to maintain a state within a request.

Transient approach => Use this approach for the lightweight service with little or no state.

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