创建 Windows Hello 登录应用

项目
07/13/2023

这是有关如何创建使用 Windows Hello 作为传统用户名和密码身份验证系统的替代方法的Windows 10和Windows 11 UWP (通用 Windows 平台) 应用的完整演练的第 1 部分。该应用将用户名用于登录并为每个帐户创建 Hello 密钥。这些帐户在配置 Windows Hello 时将受在 Windows 设置中设置的 PIN 的保护。

本演练分为两个部分：生成应用和连接后端服务。当你完成此文章时，请继续执行第 2 部分：Windows Hello 登录服务。

在开始之前，你应阅读 Windows Hello 概述，以便大致了解 Windows Hello 的工作原理。

入门

为了生成此项目，你需要具有 C# 和 XAML 方面的一些经验。还需要在Windows 10或Windows 11计算机上使用 Visual Studio 2015 (Community Edition 或更高版本) 或更高版本的 Visual Studio。尽管 Visual Studio 2015 是所需的最低版本，但我们建议将最新版本的 Visual Studio 用于最新的开发人员和安全更新。

打开 Visual Studio 并选择“文件”>“新建”>“项目”。
这将打开一个“新建项目”窗口。导航到“模板”>“Visual C#”。
选择“空白应用（通用 Windows）”并将你的应用程序命名为“PassportLogin”。
生成并运行新的应用程序 (F5)，然后你应该看到屏幕上显示的空白窗口。关闭该应用程序。

Windows Hello 新项目

在本练习中，你将了解如何检查 Windows Hello 是否在计算机上设置，以及如何使用 Windows Hello 登录到某一帐户。

在新项目中，在解决方案中创建一个名为“Views”的新文件夹。在本示例中，此文件夹包含将导航到的页面。在“解决方案资源管理器”中右键单击该项目、依次选择“添加”>“新文件夹”，然后将该文件夹重命名为 Views。
右键单击新的 Views 文件夹、依次选择“添加”>“新项目”，然后选择“空白页”。将此页面命名为“Login.xaml”。

若要为新的登录页定义用户界面，请添加以下 XAML。此 XAML 定义 StackPanel 以便对齐以下子元素：

将包含标题的 TextBlock。
用于错误消息的 TextBlock。
用于要输入的用户名的文本框。
用于导航至注册页的按钮。
包含 Windows Hello 状态的 TextBlock。
用于解释登录页的 TextBlock（当没有任何后端或已配置的用户时）。

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
  <StackPanel Orientation="Vertical">
    <TextBlock Text="Login" FontSize="36" Margin="4" TextAlignment="Center"/>
    <TextBlock x:Name="ErrorMessage" Text="" FontSize="20" Margin="4" Foreground="Red" TextAlignment="Center"/>
    <TextBlock Text="Enter your username below" Margin="0,0,0,20"
               TextWrapping="Wrap" Width="300"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>
    <TextBox x:Name="UsernameTextBox" Margin="4" Width="250"/>
    <Button x:Name="PassportSignInButton" Content="Login" Background="DodgerBlue" Foreground="White"
        Click="PassportSignInButton_Click" Width="80" HorizontalAlignment="Center" Margin="0,20"/>
    <TextBlock Text="Don't have an account?"
                TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>
    <TextBlock x:Name="RegisterButtonTextBlock" Text="Register now"
               PointerPressed="RegisterButtonTextBlock_OnPointerPressed"
               Foreground="DodgerBlue"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>
    <Border x:Name="PassportStatus" Background="#22B14C"
               Margin="0,20" Height="100" >
      <TextBlock x:Name="PassportStatusText" Text="Microsoft Passport is ready to use!"
             Margin="4" TextAlignment="Center" VerticalAlignment="Center" FontSize="20"/>
    </Border>
    <TextBlock x:Name="LoginExplaination" FontSize="24" TextAlignment="Center" TextWrapping="Wrap" 
        Text="Please Note: To demonstrate a login, validation will only occur using the default username 'sampleUsername'"/>
  </StackPanel>
</Grid>

需要将几个方法添加到代码隐藏，以便生成解决方案。按 F7，或者使用“解决方案资源管理器”来访问 Login.xaml.cs。添加以下两个事件方法，以处理登录和注册事件。现在，这些方法将 ErrorMessage.Text 设置为空字符串。

namespace PassportLogin.Views
{
    public sealed partial class Login : Page
    {
        public Login()
        {
            this.InitializeComponent();
        }

        private void PassportSignInButton_Click(object sender, RoutedEventArgs e)
        {
            ErrorMessage.Text = "";
        }
        private void RegisterButtonTextBlock_OnPointerPressed(object sender, PointerRoutedEventArgs e)
        {
            ErrorMessage.Text = "";
        }
    }
}

若要呈现登录页，可在加载 MainPage 时编辑 MainPage 代码以导航到登录页。打开 MainPage.xaml.cs 文件。在“解决方案资源管理器”中，双击 MainPage.xaml.cs。如果你找不到此文件，请单击 MainPage.xaml 旁边的小箭头以显示代码隐藏。创建将导航到登录页的已加载事件处理程序方法。你将需要添加对 Views 命名空间的引用。
```
using PassportLogin.Views;

namespace PassportLogin
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            Loaded += MainPage_Loaded;
        }

        private void MainPage_Loaded(object sender, RoutedEventArgs e)
        {
            Frame.Navigate(typeof(Login));
        }
    }
}
```

在登录页中，你需要处理 OnNavigatedTo 事件来验证 Windows Hello 在此计算机上是否可用。在 Login.xaml.cs 中，实现以下项。你会注意到 MicrosoftPassportHelper 对象标记一个错误。这是因为我们尚未实现它。

public sealed partial class Login : Page
{
    public Login()
    {
        this.InitializeComponent();
    }

    protected override async void OnNavigatedTo(NavigationEventArgs e)
    {
        // Check Microsoft Passport is setup and available on this machine
        if (await MicrosoftPassportHelper.MicrosoftPassportAvailableCheckAsync())
        {
        }
        else
        {
            // Microsoft Passport is not setup so inform the user
            PassportStatus.Background = new SolidColorBrush(Windows.UI.Color.FromArgb(255, 50, 170, 207));
            PassportStatusText.Text = "Microsoft Passport is not setup!\n" + 
                "Please go to Windows Settings and set up a PIN to use it.";
            PassportSignInButton.IsEnabled = false;
        }
    }
}

若要创建 MicrosoftPassportHelper 类，请右键单击解决方案 PassportLogin（通用 Windows），然后依次单击“添加”>“新文件夹”。将此文件夹命名为 Utils。
右键单击 Utils 文件夹，然后依次单击“添加”>“类”。将此类命名为“MicrosoftPassportHelper.cs”。

将 MicrosoftPassportHelper 的类定义更改为公共静态，然后添加以下方法以通知用户 Windows Hello 是否可供使用。你将需要添加所需的命名空间。

using System;
using System.Diagnostics;
using System.Threading.Tasks;
using Windows.Security.Credentials;

namespace PassportLogin.Utils
{
    public static class MicrosoftPassportHelper
    {
        /// <summary>
        /// Checks to see if Passport is ready to be used.
        /// 
        /// Passport has dependencies on:
        ///     1. Having a connected Microsoft Account
        ///     2. Having a Windows PIN set up for that _account on the local machine
        /// </summary>
        public static async Task<bool> MicrosoftPassportAvailableCheckAsync()
        {
            bool keyCredentialAvailable = await KeyCredentialManager.IsSupportedAsync();
            if (keyCredentialAvailable == false)
            {
                // Key credential is not enabled yet as user 
                // needs to connect to a Microsoft Account and select a PIN in the connecting flow.
                Debug.WriteLine("Microsoft Passport is not setup!\nPlease go to Windows Settings and set up a PIN to use it.");
                return false;
            }

            return true;
        }
    }
}

在 Login.xaml.cs 中，添加对 Utils 命名空间的引用。这将解决 OnNavigatedTo 方法中的错误。
```
using PassportLogin.Utils;
```
生成并运行应用程序 (F5)。你将导航到登录页，Windows Hello 横幅将指示 Hello 是否可供使用。你应该看到绿色或蓝色横幅，这指示你的计算机上的 Windows Hello 状态。
接下来你需要执行的操作是生成用于登录的逻辑。创建名为“Models”的新文件夹。
在 Models 文件夹中，创建名为“Account.cs”的新类。此类将用作你的帐户模型。由于这是一个示例，因此它将仅包含一个用户名。将类定义更改为公共，并添加 Username 属性。
```
namespace PassportLogin.Models
{
    public class Account
    {
        public string Username { get; set; }
    }
}
```

你将需要一种帐户处理方法。对于本动手实验，由于没有服务器或数据库，因此将本地保存和加载用户列表。右键单击 Utils 文件夹，然后添加名为“AccountHelper.cs”的新类。将类定义更改为公共静态。 AccountHelper 为静态类，其中包含本地保存和加载帐户列表的所有必需方法。使用 XmlSerializer 即可进行保存和加载。你还需要记住保存的文件及其保存位置。

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Serialization;
using Windows.Storage;
using PassportLogin.Models;

namespace PassportLogin.Utils
{
    public static class AccountHelper
    {
        // In the real world this would not be needed as there would be a server implemented that would host a user account database.
        // For this tutorial we will just be storing accounts locally.
        private const string USER_ACCOUNT_LIST_FILE_NAME = "accountlist.txt";
        private static string _accountListPath = Path.Combine(ApplicationData.Current.LocalFolder.Path, USER_ACCOUNT_LIST_FILE_NAME);
        public static List<Account> AccountList = new List<Account>();

        /// <summary>
        /// Create and save a useraccount list file. (Updating the old one)
        /// </summary>
        private static async void SaveAccountListAsync()
        {
            string accountsXml = SerializeAccountListToXml();

            if (File.Exists(_accountListPath))
            {
                StorageFile accountsFile = await StorageFile.GetFileFromPathAsync(_accountListPath);
                await FileIO.WriteTextAsync(accountsFile, accountsXml);
            }
            else
            {
                StorageFile accountsFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(USER_ACCOUNT_LIST_FILE_NAME);
                await FileIO.WriteTextAsync(accountsFile, accountsXml);
            }
        }

        /// <summary>
        /// Gets the useraccount list file and deserializes it from XML to a list of useraccount objects.
        /// </summary>
        /// <returns>List of useraccount objects</returns>
        public static async Task<List<Account>> LoadAccountListAsync()
        {
            if (File.Exists(_accountListPath))
            {
                StorageFile accountsFile = await StorageFile.GetFileFromPathAsync(_accountListPath);

                string accountsXml = await FileIO.ReadTextAsync(accountsFile);
                DeserializeXmlToAccountList(accountsXml);
            }

            return AccountList;
        }

        /// <summary>
        /// Uses the local list of accounts and returns an XML formatted string representing the list
        /// </summary>
        /// <returns>XML formatted list of accounts</returns>
        public static string SerializeAccountListToXml()
        {
            XmlSerializer xmlizer = new XmlSerializer(typeof(List<Account>));
            StringWriter writer = new StringWriter();
            xmlizer.Serialize(writer, AccountList);

            return writer.ToString();
        }

        /// <summary>
        /// Takes an XML formatted string representing a list of accounts and returns a list object of accounts
        /// </summary>
        /// <param name="listAsXml">XML formatted list of accounts</param>
        /// <returns>List object of accounts</returns>
        public static List<Account> DeserializeXmlToAccountList(string listAsXml)
        {
            XmlSerializer xmlizer = new XmlSerializer(typeof(List<Account>));
            TextReader textreader = new StreamReader(new MemoryStream(Encoding.UTF8.GetBytes(listAsXml)));

            return AccountList = (xmlizer.Deserialize(textreader)) as List<Account>;
        }
    }
}

接下来，实现一种可从帐户的本地列表添加和删除帐户的方法。每次执行这些操作都将保存该列表。你将需要对本动手实验执行的最终方法是验证方法。因为没有用户的身份验证服务器或数据库，因此这将对硬编码的单个用户进行验证。这些方法应添加到 AccountHelper 类。

public static Account AddAccount(string username)
        {
            // Create a new account with the username
            Account account = new Account() { Username = username };
            // Add it to the local list of accounts
            AccountList.Add(account);
            // SaveAccountList and return the account
            SaveAccountListAsync();
            return account;
        }

        public static void RemoveAccount(Account account)
        {
            // Remove the account from the accounts list
            AccountList.Remove(account);
            // Re save the updated list
            SaveAccountListAsync();
        }

        public static bool ValidateAccountCredentials(string username)
        {
            // In the real world, this method would call the server to authenticate that the account exists and is valid.
            // For this tutorial however we will just have a existing sample user that is just "sampleUsername"
            // If the username is null or does not match "sampleUsername" it will fail validation. In which case the user should register a new passport user

            if (string.IsNullOrEmpty(username))
            {
                return false;
            }

            if (!string.Equals(username, "sampleUsername"))
            {
                return false;
            }

            return true;
        }

接下来你需要执行的操作是处理来自用户的登录请求。在 Login.xaml.cs 中，创建一个将保存当前正在登录的帐户的新私有变量。然后，添加一个名为 SignInPassport 的新方法。这将使用 AccountHelper.ValidateAccountCredentials 方法验证帐户凭据。如果输入的用户名与你在上一步中设置的硬编码字符串值相同，此方法将返回一个布尔值。在本示例中，硬编码的值是“sampleUsername”。

using PassportLogin.Models;
using PassportLogin.Utils;
using System.Diagnostics;

namespace PassportLogin.Views
{
    public sealed partial class Login : Page
    {
        private Account _account;

        public Login()
        {
            this.InitializeComponent();
        }

        protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            // Check Microsoft Passport is setup and available on this machine
            if (await MicrosoftPassportHelper.MicrosoftPassportAvailableCheckAsync())
            {
            }
            else
            {
                // Microsoft Passport is not setup so inform the user
                PassportStatus.Background = new SolidColorBrush(Windows.UI.Color.FromArgb(255, 50, 170, 207));
                PassportStatusText.Text = "Microsoft Passport is not setup!\nPlease go to Windows Settings and set up a PIN to use it.";
                PassportSignInButton.IsEnabled = false;
            }
        }

        private void PassportSignInButton_Click(object sender, RoutedEventArgs e)
        {
            ErrorMessage.Text = "";
            SignInPassport();
        }

        private void RegisterButtonTextBlock_OnPointerPressed(object sender, PointerRoutedEventArgs e)
        {
            ErrorMessage.Text = "";
        }

        private async void SignInPassport()
        {
            if (AccountHelper.ValidateAccountCredentials(UsernameTextBox.Text))
            {
                // Create and add a new local account
                _account = AccountHelper.AddAccount(UsernameTextBox.Text);
                Debug.WriteLine("Successfully signed in with traditional credentials and created local account instance!");

                //if (await MicrosoftPassportHelper.CreatePassportKeyAsync(UsernameTextBox.Text))
                //{
                //    Debug.WriteLine("Successfully signed in with Microsoft Passport!");
                //}
            }
            else
            {
                ErrorMessage.Text = "Invalid Credentials";
            }
        }
    }
}

你可能已经注意到，注释代码引用了 MicrosoftPassportHelper 中的方法。在 MicrosoftPassportHelper.cs 中，添加名为 CreatePassportKeyAsync 的新方法。此方法使用 KeyCredentialManager 中的 Windows Hello API。调用 RequestCreateAsync 将创建特定于 accountId 和本地计算机的 Passport 密钥。如果你对在真实应用场景中进行实现感兴趣，请注意 switch 语句中的注释。

/// <summary>
/// Creates a Passport key on the machine using the _account id passed.
/// </summary>
/// <param name="accountId">The _account id associated with the _account that we are enrolling into Passport</param>
/// <returns>Boolean representing if creating the Passport key succeeded</returns>
public static async Task<bool> CreatePassportKeyAsync(string accountId)
{
    KeyCredentialRetrievalResult keyCreationResult = await KeyCredentialManager.RequestCreateAsync(accountId, KeyCredentialCreationOption.ReplaceExisting);

    switch (keyCreationResult.Status)
    {
        case KeyCredentialStatus.Success:
            Debug.WriteLine("Successfully made key");

            // In the real world authentication would take place on a server.
            // So every time a user migrates or creates a new Microsoft Passport account Passport details should be pushed to the server.
            // The details that would be pushed to the server include:
            // The public key, keyAttesation if available, 
            // certificate chain for attestation endorsement key if available,  
            // status code of key attestation result: keyAttestationIncluded or 
            // keyAttestationCanBeRetrievedLater and keyAttestationRetryType
            // As this sample has no concept of a server it will be skipped for now
            // for information on how to do this refer to the second Passport sample

            //For this sample just return true
            return true;
        case KeyCredentialStatus.UserCanceled:
            Debug.WriteLine("User cancelled sign-in process.");
            break;
        case KeyCredentialStatus.NotFound:
            // User needs to setup Microsoft Passport
            Debug.WriteLine("Microsoft Passport is not setup!\nPlease go to Windows Settings and set up a PIN to use it.");
            break;
        default:
            break;
    }

    return false;
}

现在你已创建 CreatePassportKeyAsync 方法，请返回到 Login.xaml.cs 文件，并取消对 SignInPassport 方法内代码的注释。

private async void SignInPassport()
{
    if (AccountHelper.ValidateAccountCredentials(UsernameTextBox.Text))
    {
        //Create and add a new local account
        _account = AccountHelper.AddAccount(UsernameTextBox.Text);
        Debug.WriteLine("Successfully signed in with traditional credentials and created local account instance!");

        if (await MicrosoftPassportHelper.CreatePassportKeyAsync(UsernameTextBox.Text))
        {
            Debug.WriteLine("Successfully signed in with Microsoft Passport!");
        }
    }
    else
    {
        ErrorMessage.Text = "Invalid Credentials";
    }
}

生成并运行应用程序。你将转到登录页。键入“sampleUsername”，然后单击“登录”。系统将通过一条 Windows Hello 提示信息提示你输入 PIN。在正确输入 PIN 之后，CreatePassportKeyAsync 方法将能够创建 Windows Hello 密钥。监视输出窗口，以查看是否显示指示已成功的消息。

练习 2：欢迎页和用户选择页

在本练习中，你将从上一练习继续操作。当用户成功登录时，他们应该进入可从中注销或删除其帐户的欢迎页。当 Windows Hello 为每台计算机创建密钥时，将创建一个用户选择屏幕，该屏幕上将显示已登录这台计算机的所有用户。然后，用户可以选择这些帐户之一并直接转至欢迎屏幕，而无需重新输入密码，因为已针对这些用户进行身份验证，以便访问该计算机。

在 Views 文件夹中，添加名为“Welcome.xaml”的新空白页。添加以下 XAML 来完成用户界面。这将显示一个标题、登录的用户名以及两个按钮。其中一个按钮将向后导航到用户列表（将在稍后创建），另一个按钮将处理忘记此用户的情况。

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
  <StackPanel Orientation="Vertical">
    <TextBlock x:Name="Title" Text="Welcome" FontSize="40" TextAlignment="Center"/>
    <TextBlock x:Name="UserNameText" FontSize="28" TextAlignment="Center" Foreground="Black"/>

    <Button x:Name="BackToUserListButton" Content="Back to User List" Click="Button_Restart_Click"
            HorizontalAlignment="Center" Margin="0,20" Foreground="White" Background="DodgerBlue"/>

    <Button x:Name="ForgetButton" Content="Forget Me" Click="Button_Forget_User_Click"
            Foreground="White"
            Background="Gray"
            HorizontalAlignment="Center"/>
  </StackPanel>
</Grid>

在 Welcome.xaml.cs 代码隐藏文件中，添加用于保留已登录的帐户的新私有变量。你将需要实现某种方法来替代 OnNavigateTo 事件，以便存储传递至欢迎页的帐户。还需要针对 XAML 中定义的两个按钮实现单击事件。你将需要一个对 Models 和 Utils 文件夹的引用。

using PassportLogin.Models;
using PassportLogin.Utils;
using System.Diagnostics;

namespace PassportLogin.Views
{
    public sealed partial class Welcome : Page
    {
        private Account _activeAccount;

        public Welcome()
        {
            InitializeComponent();
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            _activeAccount = (Account)e.Parameter;
            if (_activeAccount != null)
            {
                UserNameText.Text = _activeAccount.Username;
            }
        }

        private void Button_Restart_Click(object sender, RoutedEventArgs e)
        {
        }

        private void Button_Forget_User_Click(object sender, RoutedEventArgs e)
        {
            // Remove it from Microsoft Passport
            // MicrosoftPassportHelper.RemovePassportAccountAsync(_activeAccount);

            // Remove it from the local accounts list and resave the updated list
            AccountHelper.RemoveAccount(_activeAccount);

            Debug.WriteLine("User " + _activeAccount.Username + " deleted.");
        }
    }
}

你可能已注意到，某行在忘记用户单击事件中已有注释。该帐户将从你的本地列表中删除，不过当前没有从 Windows Hello 删除的方法。你需要在 MicrosoftPassportHelper.cs 中实现一个新方法，以便处理 Windows Hello 用户的删除操作。此方法将使用其他 Windows Hello API 打开和删除该帐户。实际上，在删除帐户后，应通知服务器或数据库，以便用户数据库保持有效。你将需要一个对 Models 文件夹的引用。

using PassportLogin.Models;

/// <summary>
/// Function to be called when user requests deleting their account.
/// Checks the KeyCredentialManager to see if there is a Passport for the current user
/// Then deletes the local key associated with the Passport.
/// </summary>
public static async void RemovePassportAccountAsync(Account account)
{
    // Open the account with Passport
    KeyCredentialRetrievalResult keyOpenResult = await KeyCredentialManager.OpenAsync(account.Username);

    if (keyOpenResult.Status == KeyCredentialStatus.Success)
    {
        // In the real world you would send key information to server to unregister
        //for example, RemovePassportAccountOnServer(account);
    }

    // Then delete the account from the machines list of Passport Accounts
    await KeyCredentialManager.DeleteAsync(account.Username);
}

返回到 Welcome.xaml.cs，并取消用于调用 RemovePassportAccountAsync 的行的注释。

private void Button_Forget_User_Click(object sender, RoutedEventArgs e)
{
    // Remove it from Microsoft Passport
    MicrosoftPassportHelper.RemovePassportAccountAsync(_activeAccount);

    // Remove it from the local accounts list and resave the updated list
    AccountHelper.RemoveAccount(_activeAccount);

    Debug.WriteLine("User " + _activeAccount.Username + " deleted.");
}

在 SignInPassport 方法（属于 Login.xaml.cs）中，在CreatePassportKeyAsync 成功创建后，应导航到欢迎屏幕并传递该帐户。

private async void SignInPassport()
{
    if (AccountHelper.ValidateAccountCredentials(UsernameTextBox.Text))
    {
        // Create and add a new local account
        _account = AccountHelper.AddAccount(UsernameTextBox.Text);
        Debug.WriteLine("Successfully signed in with traditional credentials and created local account instance!");

        if (await MicrosoftPassportHelper.CreatePassportKeyAsync(UsernameTextBox.Text))
        {
            Debug.WriteLine("Successfully signed in with Microsoft Passport!");
            Frame.Navigate(typeof(Welcome), _account);
        }
    }
    else
    {
        ErrorMessage.Text = "Invalid Credentials";
    }
}

生成并运行应用程序。使用“sampleUsername”登录，然后单击“登录”。输入你的 PIN，如果成功，你应导航到欢迎屏幕。尝试单击“忘记用户”，并监视输出窗口以查看是否已删除该用户。请注意，在用户删除后，你将仍位于欢迎页上。你需要创建应用可以导航到的用户选择页。

在 Views 文件夹中，创建名为“UserSelection.xaml”的新空白页，然后添加以下 XAML 来定义用户界面。此页面将包含一个用于在本地帐户列表中显示所有用户的 ListView，以及一个用于导航到登录页的 Button，从而让用户可以添加其他帐户。

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
  <StackPanel Orientation="Vertical">
    <TextBlock x:Name="Title" Text="Select a User" FontSize="36" Margin="4" TextAlignment="Center" HorizontalAlignment="Center"/>

    <ListView x:Name="UserListView" Margin="4" MaxHeight="200" MinWidth="250" Width="250" HorizontalAlignment="Center">
      <ListView.ItemTemplate>
        <DataTemplate>
          <Grid Background="DodgerBlue" Height="50" Width="250" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
            <TextBlock Text="{Binding Username}" HorizontalAlignment="Center" TextAlignment="Center" VerticalAlignment="Center" Foreground="White"/>
          </Grid>
        </DataTemplate>
      </ListView.ItemTemplate>
    </ListView>

    <Button x:Name="AddUserButton" Content="+" FontSize="36" Width="60" Click="AddUserButton_Click" HorizontalAlignment="Center"/>
  </StackPanel>
</Grid>

在 UserSelection.xaml.cs 中，如果本地列表中不存在任何帐户，则实现将导航到登录页的加载方法。此外，针对 ListView 实现 SelectionChanged 事件，针对 Button 实现单击事件。

using System.Diagnostics;
using PassportLogin.Models;
using PassportLogin.Utils;

namespace PassportLogin.Views
{
    public sealed partial class UserSelection : Page
    {
        public UserSelection()
        {
            InitializeComponent();
            Loaded += UserSelection_Loaded;
        }

        private void UserSelection_Loaded(object sender, RoutedEventArgs e)
        {
            if (AccountHelper.AccountList.Count == 0)
            {
                //If there are no accounts navigate to the LoginPage
                Frame.Navigate(typeof(Login));
            }


            UserListView.ItemsSource = AccountHelper.AccountList;
            UserListView.SelectionChanged += UserSelectionChanged;
        }

        /// <summary>
        /// Function called when an account is selected in the list of accounts
        /// Navigates to the Login page and passes the chosen account
        /// </summary>
        private void UserSelectionChanged(object sender, RoutedEventArgs e)
        {
            if (((ListView)sender).SelectedValue != null)
            {
                Account account = (Account)((ListView)sender).SelectedValue;
                if (account != null)
                {
                    Debug.WriteLine("Account " + account.Username + " selected!");
                }
                Frame.Navigate(typeof(Login), account);
            }
        }

        /// <summary>
        /// Function called when the "+" button is clicked to add a new user.
        /// Navigates to the Login page with nothing filled out
        /// </summary>
        private void AddUserButton_Click(object sender, RoutedEventArgs e)
        {
            Frame.Navigate(typeof(Login));
        }
    }
}

存在你想要在其中导航到 UserSelection 页的应用中的多个位置。在 MainPage.xaml.cs 中，你应导航到 UserSelection 页而不是登录页。当你在 MainPage 中执行加载事件时，你需要加载帐户列表，以便 UserSelection 页可以检查是否存在任何帐户。此操作不仅需要更改要异步执行的加载方法，还需要添加对 Utils 文件夹的引用。
```
using PassportLogin.Utils;

private async void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    // Load the local Accounts List before navigating to the UserSelection page
    await AccountHelper.LoadAccountListAsync();
    Frame.Navigate(typeof(UserSelection));
}
```

接下来，需要从欢迎页导航到 UserSelection 页。在这两个单击事件中，你应向后导航到 UserSelection 页。

private void Button_Restart_Click(object sender, RoutedEventArgs e)
{
    Frame.Navigate(typeof(UserSelection));
}

private void Button_Forget_User_Click(object sender, RoutedEventArgs e)
{
    // Remove it from Microsoft Passport
    MicrosoftPassportHelper.RemovePassportAccountAsync(_activeAccount);

    // Remove it from the local accounts list and resave the updated list
    AccountHelper.RemoveAccount(_activeAccount);

    Debug.WriteLine("User " + _activeAccount.Username + " deleted.");

    // Navigate back to UserSelection page.
    Frame.Navigate(typeof(UserSelection));
}

在登录页中，你需要代码来登录到从 UserSelection 页的列表中选择的帐户。在 OnNavigatedTo 事件中，存储已传递给导航的帐户。首先，添加新的私有变量，用于标识帐户是否为现有帐户。然后，处理 OnNavigatedTo 事件。

namespace PassportLogin.Views
{
    public sealed partial class Login : Page
    {
        private Account _account;
        private bool _isExistingAccount;

        public Login()
        {
            InitializeComponent();
        }

        /// <summary>
        /// Function called when this frame is navigated to.
        /// Checks to see if Microsoft Passport is available and if an account was passed in.
        /// If an account was passed in set the "_isExistingAccount" flag to true and set the _account
        /// </summary>
        protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            // Check Microsoft Passport is setup and available on this machine
            if (await MicrosoftPassportHelper.MicrosoftPassportAvailableCheckAsync())
            {
                if (e.Parameter != null)
                {
                    _isExistingAccount = true;
                    // Set the account to the existing account being passed in
                    _account = (Account)e.Parameter;
                    UsernameTextBox.Text = _account.Username;
                    SignInPassport();
                }
            }
            else
            {
                // Microsoft Passport is not setup so inform the user
                PassportStatus.Background = new SolidColorBrush(Windows.UI.Color.FromArgb(255, 50, 170, 207));
                PassportStatusText.Text = "Microsoft Passport is not setup!\n" + 
                    "Please go to Windows Settings and set up a PIN to use it.";
                PassportSignInButton.IsEnabled = false;
            }
        }
    }
}

SignInPassport 方法将需要进行更新，以便登录到所选的帐户。 MicrosoftPassportHelper 将需要另一种方法来使用 Passport 打开帐户，因为帐户已具有一个为其创建的 Passport 密钥。在 MicrosoftPassportHelper.cs 中实现新方法，以便现有用户可以使用 Passport 登录。有关代码的每个部分的信息，请阅读整个代码注释。

/// <summary>
/// Attempts to sign a message using the Passport key on the system for the accountId passed.
/// </summary>
/// <returns>Boolean representing if creating the Passport authentication message succeeded</returns>
public static async Task<bool> GetPassportAuthenticationMessageAsync(Account account)
{
    KeyCredentialRetrievalResult openKeyResult = await KeyCredentialManager.OpenAsync(account.Username);
    // Calling OpenAsync will allow the user access to what is available in the app and will not require user credentials again.
    // If you wanted to force the user to sign in again you can use the following:
    // var consentResult = await Windows.Security.Credentials.UI.UserConsentVerifier.RequestVerificationAsync(account.Username);
    // This will ask for the either the password of the currently signed in Microsoft Account or the PIN used for Microsoft Passport.

    if (openKeyResult.Status == KeyCredentialStatus.Success)
    {
        // If OpenAsync has succeeded, the next thing to think about is whether the client application requires access to backend services.
        // If it does here you would Request a challenge from the Server. The client would sign this challenge and the server
        // would check the signed challenge. If it is correct it would allow the user access to the backend.
        // You would likely make a new method called RequestSignAsync to handle all this
        // for example, RequestSignAsync(openKeyResult);
        // Refer to the second Microsoft Passport sample for information on how to do this.

        // For this sample there is not concept of a server implemented so just return true.
        return true;
    }
    else if (openKeyResult.Status == KeyCredentialStatus.NotFound)
    {
        // If the _account is not found at this stage. It could be one of two errors. 
        // 1. Microsoft Passport has been disabled
        // 2. Microsoft Passport has been disabled and re-enabled cause the Microsoft Passport Key to change.
        // Calling CreatePassportKey and passing through the account will attempt to replace the existing Microsoft Passport Key for that account.
        // If the error really is that Microsoft Passport is disabled then the CreatePassportKey method will output that error.
        if (await CreatePassportKeyAsync(account.Username))
        {
            // If the Passport Key was again successfully created, Microsoft Passport has just been reset.
            // Now that the Passport Key has been reset for the _account retry sign in.
            return await GetPassportAuthenticationMessageAsync(account);
        }
    }

    // Can't use Passport right now, try again later
    return false;
}

在 Login.xaml.cs 中更新 SignInPassport 方法以处理现有帐户。这将在 MicrosoftPassportHelper.cs 中使用新方法。如果成功，将登录该帐户，并且用户将导航到欢迎屏幕。

private async void SignInPassport()
{
    if (_isExistingAccount)
    {
        if (await MicrosoftPassportHelper.GetPassportAuthenticationMessageAsync(_account))
        {
            Frame.Navigate(typeof(Welcome), _account);
        }
    }
    else if (AccountHelper.ValidateAccountCredentials(UsernameTextBox.Text))
    {
        //Create and add a new local account
        _account = AccountHelper.AddAccount(UsernameTextBox.Text);
        Debug.WriteLine("Successfully signed in with traditional credentials and created local account instance!");

        if (await MicrosoftPassportHelper.CreatePassportKeyAsync(UsernameTextBox.Text))
        {
            Debug.WriteLine("Successfully signed in with Microsoft Passport!");
            Frame.Navigate(typeof(Welcome), _account);
        }
    }
    else
    {
        ErrorMessage.Text = "Invalid Credentials";
    }
}

生成并运行应用程序。使用“sampleUsername”登录。键入你的 PIN，如果成功，你将导航到欢迎屏幕。通过单击返回到用户列表。你现在应该可以在列表中看到用户。通过单击此 Passport，你可以重新登录，而无需重新输入任何密码等。

练习 3：注册新 Windows Hello 用户

在本练习中，将为你创建一个新页面，将在该页面中使用 Windows Hello 创建一个新帐户。这将与登录页的工作原理类似。登录页将针对迁移的现有用户进行实现，以便使用 Windows Hello。 PassportRegister 页将为新用户创建 Windows Hello 注册。

在 Views 文件夹中，创建名为“PassportRegister.xaml”的新空白页。在 XAML 中，添加以下内容来设置用户界面。此处的界面类似于登录页。

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
  <StackPanel Orientation="Vertical">
    <TextBlock x:Name="Title" Text="Register New Passport User" FontSize="24" Margin="4" TextAlignment="Center"/>

    <TextBlock x:Name="ErrorMessage" Text="" FontSize="20" Margin="4" Foreground="Red" TextAlignment="Center"/>

    <TextBlock Text="Enter your new username below" Margin="0,0,0,20"
               TextWrapping="Wrap" Width="300"
               TextAlignment="Center" VerticalAlignment="Center" FontSize="16"/>

    <TextBox x:Name="UsernameTextBox" Margin="4" Width="250"/>

    <Button x:Name="PassportRegisterButton" Content="Register" Background="DodgerBlue" Foreground="White"
        Click="RegisterButton_Click_Async" Width="80" HorizontalAlignment="Center" Margin="0,20"/>

    <Border x:Name="PassportStatus" Background="#22B14C"
               Margin="4" Height="100">
      <TextBlock x:Name="PassportStatusText" Text="Microsoft Passport is ready to use!" FontSize="20"
             Margin="4" TextAlignment="Center" VerticalAlignment="Center"/>
    </Border>
  </StackPanel>
</Grid>

在 PassportRegister.xaml.cs 代码隐藏文件中，实现私有 Account 变量，并针对注册 Button 实现单击事件。这将添加一个新的本地帐户，并创建 Passport 密钥。

using PassportLogin.Models;
using PassportLogin.Utils;

namespace PassportLogin.Views
{
    public sealed partial class PassportRegister : Page
    {
        private Account _account;

        public PassportRegister()
        {
            InitializeComponent();
        }

        private async void RegisterButton_Click_Async(object sender, RoutedEventArgs e)
        {
            ErrorMessage.Text = "";

            //In the real world you would normally validate the entered credentials and information before 
            //allowing a user to register a new account. 
            //For this sample though we will skip that step and just register an account if username is not null.

            if (!string.IsNullOrEmpty(UsernameTextBox.Text))
            {
                //Register a new account
                _account = AccountHelper.AddAccount(UsernameTextBox.Text);
                //Register new account with Microsoft Passport
                await MicrosoftPassportHelper.CreatePassportKeyAsync(_account.Username);
                //Navigate to the Welcome Screen. 
                Frame.Navigate(typeof(Welcome), _account);
            }
            else
            {
                ErrorMessage.Text = "Please enter a username";
            }
        }
    }
}

当单击注册时，需要从登录页导航至该页。

private void RegisterButtonTextBlock_OnPointerPressed(object sender, PointerRoutedEventArgs e)
{
    ErrorMessage.Text = "";
    Frame.Navigate(typeof(PassportRegister));
}

生成并运行应用程序。尝试注册新用户。然后返回到用户列表并验证你可以选择该用户和登录信息。

在本实验中，你已经掌握了使用新 Windows Hello API 对现有用户进行身份验证和为新用户创建帐户时所需的基本技能。借助此新知识，你的用户现在不再需要记住你的应用程序密码，不过请放心，你的应用程序仍然受用户身份验证保护。 Windows 10和Windows 11使用 Windows Hello 的新身份验证技术来支持其生物识别登录选项。

入门

练习 2：欢迎页和用户选择页

练习 3：注册新 Windows Hello 用户

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入门

练习 1：使用 Microsoft Passport 登录

练习 2：欢迎页和用户选择页

练习 3：注册新 Windows Hello 用户

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