MyAuthStateProvider.cs

public class MyAuthenticationStateProvider : AuthenticationStateProvider
{
    private readonly IAuthenticationService authService;
    private readonly IClientTokenStorage clientTokenStorage;
    private AuthenticationState currentAuthenticationState;

    public MyAuthenticationStateProvider(        
        IAuthenticationService authService,
        IClientTokenStorage clientTokenStorage)
    {
        this.authService = authService;
        this.clientTokenStorage = clientTokenStorage;
        this.authService.UserLoggedIn = async () =>
        {     
            NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
        };
        this.authService.UserLoggedOut = async () =>
        {
            await this.clientTokenStorage.RemoveToken(AuthConstants.AUTH_TOKEN_KEY);
            NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
        };
    }

    public override async Task<AuthenticationState> GetAuthenticationStateAsync()
    {
        var authToken = await clientTokenStorage.GetToken(
            AuthConstants.AUTH_TOKEN_KEY);

        if (string.IsNullOrWhiteSpace(authToken) ||
            HasTokenExpired(authToken))
        {
            await clientTokenStorage.RemoveToken(AuthConstants.AUTH_TOKEN_KEY);
            currentAuthenticationState = new AuthenticationState(
                new ClaimsPrincipal(
                    new ClaimsIdentity()));
        }
        else
        {            
            currentAuthenticationState = new AuthenticationState(
                new ClaimsPrincipal(
                    new ClaimsIdentity(
                        JwtClaimsParser.GetClaims(authToken),
                        "password")));
        }

        return currentAuthenticationState;
    }

    private bool HasTokenExpired(string authToken)
    {
        var claims = JwtClaimsParser.GetClaims(authToken);
        var expiryClaim = claims.FirstOrDefault(x => x.Type == JwtRegisteredClaimNames.Exp);
        var expiresOn = long.Parse(expiryClaim.Value);

        return DateTimeOffset.UtcNow.ToUnixTimeSeconds() > expiresOn;
    }
}