How do you implement authentication and authorization in ASP.NET Core?

In ASP.NET Core, authentication and authorization can be implemented using middleware components and ASP.NET Core Identity.

Authentication 

Authentication is the process of verifying the identity of a user. Here are the steps to implement authentication in an ASP.NET Core application:

1. Configure the authentication middleware component in the Startup.cs file. This can be done using the services.AddAuthentication() method and specifying the authentication scheme, such as cookies, tokens, or external providers.
2. Add authentication attributes to the controllers or actions that require authentication. This can be done using the [Authorize] attribute.
3. Implement the login and logout functionality in the application. This can be done using the SignInManager and UserManager classes provided by ASP.NET Core Identity.

Authorization 

Authorization is the process of determining whether a user has access to a specific resource or action. Here are the steps to implement authorization in an ASP.NET Core application:

1. Configure the authorization middleware component in the Startup.cs file. This can be done using the services.AddAuthorization() method and specifying the policy requirements.
2. Define the authorization policies in the application. This can be done using the AuthorizationPolicyBuilder class and specifying the requirements for each policy.
3. Add authorization attributes to the controllers or actions that require authorization. This can be done using the [Authorize] attribute with the policy name.
4. Implement the custom authorization requirements if necessary. This can be done by creating a class that implements the IAuthorizationRequirement interface and registering it in the application's service collection.

Overall, implementing authentication and authorization in ASP.NET Core requires a combination of middleware components, ASP.NET Core Identity, and custom code. By following the above steps, you can secure your ASP.NET Core application and ensure that users only have access to the appropriate resources and actions.