Azure AD B2C with Wpf App and Web API

MainWindow.xaml.cs

/// <summary>
/// Acquires token and then gives call to API
/// </summary>
/// <param name="sender">The sender</param>
/// <param name="e">The event arguments</param>
private async void CallApiButton_Click(object sender, RoutedEventArgs e)
{
    //// Try to Acquire token silently
    //// If not possible, then try to acquire it interactively.
    AuthenticationResult authResult = null;
    var app = App.PublicClientApp;
    IEnumerable<IAccount> accounts = await App.PublicClientApp.GetAccountsAsync();
    try
    {
        authResult = await app.AcquireTokenSilent(App.ApiScopes, GetAccountByPolicy(accounts, App.PolicySignUpSignIn))
            .ExecuteAsync();
    }
    catch (MsalUiRequiredException ex)
    {
        // A MsalUiRequiredException happened on AcquireTokenSilentAsync. 
        // This indicates you need to call AcquireTokenAsync to acquire a token
        Debug.WriteLine($"MsalUiRequiredException: {ex.Message}");

        try
        {
            authResult = await app.AcquireTokenInteractive(App.Scopes)
                .ExecuteAsync();
        }
        catch (MsalException msalex)
        {
            ResultText.Text = $"Error Acquiring Token:{Environment.NewLine}{msalex}";
        }
    }
    catch (Exception ex)
    {
        ResultText.Text = $"Error Acquiring Token Silently:{Environment.NewLine}{ex}";
        return;
    }

    //// After token is available
    //// Call the API and Show the result
    if (authResult != null)
    {
        if (string.IsNullOrEmpty(authResult.AccessToken))
        {
            ResultText.Text = "Access token is null (could be expired). Please do interactive log-in again.";
        }
        else
        {
            ResultText.Text = await GetHttpContentWithToken(App.ApiEndpoint, authResult.AccessToken);
            DisplayUserInfo(authResult);
        }
    }
}

/// <summary>
/// Perform an HTTP GET request to a URL using an HTTP Authorization header
/// </summary>
/// <param name="url">The URL</param>
/// <param name="token">The token</param>
/// <returns>String containing the results of the GET operation</returns>
public async Task<string> GetHttpContentWithToken(string url, string token)
{
    var httpClient = new HttpClient();
    HttpResponseMessage response;
    try
    {
        var request = new HttpRequestMessage(HttpMethod.Get, url);
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
        response = await httpClient.SendAsync(request);
        var content = await response.Content.ReadAsStringAsync();
        return content;
    }
    catch (Exception ex)
    {
        return ex.ToString();
    }
}