C# Microsoft Authentication Get logged user from controller

Question

So I have an Angular and C# Web API 2 app that uses Microsoft Authentication (msal.js) for the login. Now I'm trying to save data and I need the details of the current logged user. Is there a way to get the logged user from the C# Controller?

I can do this in Angular, but I think it's not secured to do it from the client side so I was thinking if maybe there was a way that the backend knows who's the logged user.

Thanks in advance!

EDIT

Startup.Auth.cs

  var tvps = new TokenValidationParameters
  {
    ValidAudience = "the id given from Microsoft Graph Registration", //xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    ValidateIssuer = false,
  };

  app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions
  {
    AccessTokenFormat = new Microsoft.Owin.Security.Jwt.JwtFormat(tvps, new OpenIdConnectCachingSecurityTokenProvider("https://login.microsoftonline.com/common/v2.0/.well-known/openid-configuration"))
  });

frontend-login.ts

let userAgentApp = new UserAgentApplication(clientId, null,
    (errorDes: any, token: any, error: any, tokenType: any) => {
        userAgentApp.acquireTokenSilent(["user.read"]).then((token: string) => {});
    }, { redirectUri: 'http://localhost:port/signin-microsoft' });
userAgentApp.loginPopup(["user.read"]).then((token: string) => {
    //store the token and redirect to home page
});

EDIT

I am using it when accessing the API like this:

this.headers.append('Authorization', 'Bearer ' + sessionStorage.getItem('token'));
this.http.get(`${this.url}`, { headers: this.headers })
  .map((response: Response) => { return response.json() })

FINAL EDIT

I posted another question regarding this and this problem was answered there. I am posting the link below in case someone needs it in the future:

C# Web API 2 & Angular - Microsoft Account Authentication

Answer 1

In Web Api, you need to read the Bearer Token. Here is a tutorial on the subject as a whole, but the gist of it is to use UseOAuthBearerAuthentication in your startup class when setup up the owin pipeline, this will enable access in controllers when calling RequestContext.Principal .

public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            ConfigureOAuth(app);
        //Rest of code is here;
        }

        public void ConfigureOAuth(IAppBuilder app)
        {
            OAuthAuthorizationServerOptions OAuthServerOptions = new OAuthAuthorizationServerOptions()
            {
                AllowInsecureHttp = true,
                TokenEndpointPath = new PathString("/token"),
                AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
                Provider = new SimpleAuthorizationServerProvider()
            };

            // Token Generation
            app.UseOAuthAuthorizationServer(OAuthServerOptions);
            app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());

        }
    }