When we use AddScoped, AddSingleton, and AddTransient ?

In ASP.NET Core, dependency injection (DI) is a fundamental concept that allows you to manage the lifetime of services. The methods AddScoped(), AddTransient(), and AddSingleton() are used to register services with different lifetimes. Here’s a breakdown of each:

1. AddTransient():

   • Lifetime: Transient services are created each time they are requested. This means that every time a service is injected, a new instance is provided.
   • Use Case: Use AddTransient() for lightweight, stateless services where you want a new instance for each request. For example, services that perform operations that do not maintain state between requests.
      

     services.AddTransient();

2.  AddScoped(): 

   • Lifetime: Scoped services are created once per request (or per scope). This means that within a single request, the same instance is used, but a new instance is created for each new request.

   • Use Case: Use AddScoped() for services that need to maintain state during a single request but should not share state across different requests. This is commonly used for database contexts.
      

     services.AddScoped();
     

3. AddSingleton():

   • Lifetime: Singleton services are created once and shared throughout the application's lifetime. The same instance is used for all requests and all users.
   • Use Case: Use AddSingleton() for services that are expensive to create and do not maintain any state that is specific to a user or request. This is suitable for services that are stateless or that can safely share state across requests.
      

     services.AddSingleton();
     

      

???????IMP Points to know

• AddTransient(): New instance every time it is requested.
• AddScoped(): New instance per request.
• AddSingleton(): Single instance for the entire application lifetime.