Token-based authentication

Token-based authentication is a widely used approach to secure web APIs. It involves the client application sending a request to the authentication server with valid credentials. The authentication server responds with an access token that contains enough data to identify a particular user and has an expiry time. The client application then uses the token to access restricted resources in subsequent requests until the token is valid. If the access token is expired, the client application can request a new access token by using a refresh token 1.

In C#, you can implement token-based authentication in Web APIs using OAuth. OAuth is an open standard for token-based authentication and authorization on the internet 1. Here are some steps to implement token-based authentication in Web APIs using OAuth:

1. Create an ASP.NET Web project in Visual Studio 2019.
2. Add NuGet references like Microsoft.Owin.Host.SystemWeb, Microsoft.Owin.Security.OAuth, and Microsoft.Owin.Cors.
3. Create an ApiAuthorizationServerProvider.cs class file to provide credentials to access data depending on username, password, and roles 1.
4. Use OAuth authentication to create a token-based authentication API 1.

You can also use HTTP authentication schemes (Basic & Bearer), API keys, or OpenID Connect for Web API authentication 1.