Angular 2 and .NET Web API Authentication
First of all try to avoid using self implemented methods.
Most commonly used approach is to use Json web token
.
https://jwt.io/
There for when you log in, return Token to angular2 and then pass it on every request.
There are many examples of implementation and libraries to be used.
https://github.com/auth0/angular2-jwt
How to use JWT in MVC application for authentication and authorization?