part of Startup.cs for auth code flow with Owin and ASP.NET

Snippet from Startup.cs

app.UseOpenIdConnectAuthentication(new OpenIdConnectAuthenticationOptions
{
    ClientId = clientId,
    ClientSecret = clientSecret,
    Authority = authority,
    MetadataAddress = metaDataUri,
    RedirectUri = redirectUri,
    ResponseType = OpenIdConnectResponseType.Code,
    Scope = OpenIdConnectScope.OpenId,
    PostLogoutRedirectUri = postLogoutRedirectUri,
    TokenValidationParameters = new TokenValidationParameters
    {
        NameClaimType = "name"
    },
    Notifications = new OpenIdConnectAuthenticationNotifications
    {
        AuthorizationCodeReceived = ProcessAuthorizationCodeReceivedNotification,
        RedirectToIdentityProvider = ProcessRedirectToIdentityProviderNotification,
        MessageReceived = ProcessMessageReceivedNotification
    },
});

List<Claim> claims = new List<Claim>();
private async Task ProcessMessageReceivedNotification(MessageReceivedNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> args)
{
    if (!string.IsNullOrWhiteSpace(args.ProtocolMessage.Code))
    {
        var openIdConfiguration = await args.Options.ConfigurationManager.GetConfigurationAsync(new CancellationToken()).ConfigureAwait(false);

        // Exchange code for access and ID tokens
        var tokenClient = new TokenClient(openIdConfiguration.TokenEndpoint, clientId, clientSecret);
        var tokenResponse = await tokenClient.RequestAuthorizationCodeAsync(args.ProtocolMessage.Code, redirectUri);

        if (tokenResponse.IsError)
        {
            throw new Exception(tokenResponse.Error);
        }

        var userInfoClient = new UserInfoClient(openIdConfiguration.UserInfoEndpoint);
        var userInfoResponse = await userInfoClient.GetAsync(tokenResponse.AccessToken);
        args.ProtocolMessage.IdToken = tokenResponse.IdentityToken;
        //args.ProtocolMessage.AccessToken = tokenResponse.AccessToken;
        //args.ProtocolMessage.RefreshToken = tokenResponse.RefreshToken;
        claims.AddRange(userInfoResponse.Claims);

        claims.AddRange(userInfoResponse.Claims);
        claims.Add(new Claim("id_token", tokenResponse.IdentityToken));
        claims.Add(new Claim("access_token", tokenResponse.AccessToken));

        if (!string.IsNullOrEmpty(tokenResponse.RefreshToken))
        {
            claims.Add(new Claim("refresh_token", tokenResponse.RefreshToken));
        }
    }
}

private Task ProcessAuthorizationCodeReceivedNotification(AuthorizationCodeReceivedNotification args)
{
    if (args.AuthenticationTicket != null)
        args.AuthenticationTicket.Identity.AddClaims(claims);

    return Task.FromResult(0);
}