c# - 使用MVVM(无任何代码)且无导航时，单击按钮时更改 View

Question

我正在使用WPF MVVM。

我有一个WCF聊天服务，该服务应执行某些验证操作(用户凭据)才能将消息发送到聊天窗口。

当然，这是在我按下“登录!”按钮时发生的。

我要完成的事情是在我按下登录并成功通过验证后的新 View (“聊天窗口” View )。

*由于我还没有聊天 View ，因此假设我的聊天 View 是我的注册 View (仅出于了解如何使用ICommand进行按钮单击时切换 View 的原理)

我将发布已完成的操作:

MainWindow.xaml:

    <Window.Resources>
    <DataTemplate DataType="{x:Type  ViewModels:LoginViewModel}">
        <Views:LoginView />
    </DataTemplate>
    <DataTemplate DataType="{x:Type ViewModels:SignUpViewModel}">
        <Views:SignUpView />
    </DataTemplate>
</Window.Resources>
<Grid>
    <ContentControl Content="{Binding CurrentView}" />
</Grid>

MainWindow.xaml.cs:

    public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new AppViewModel();
    }
}

LoginViewModel.cs

    public class LoginViewModel : ViewModelBase
{
    public AuthenticatedUser AuthenticatedUser { get; set; }
    private string username;

    public string UserName
    {
        get { return username; }
        set {
            username = value;
            Notify();
        }
    }
    private string password;
    public string Password
    {
        get { return password; }
        set
        {
            password = value;
            Notify();
        }
    }

    public ConsoleLog ConsoleLog { get ; set; } // TODO: StringBuilder.
    public UserServiceProxy UserServiceProxy { get; set; }
    public ChatServiceProxy ChatServiceProxy { get; set; }

    public LoginViewModel()
    {
        AuthenticatedUser = AuthenticatedUser.Instance;
        UserServiceProxy = new UserServiceProxy();
        ChatServiceProxy = new ChatServiceProxy();
        SendLoginRequestCommand = new MyCommand(SendLoginRequest);
        ConsoleLog = new ConsoleLog();
        ConsoleLog.Document = "Binding Checker.";
    }

    public ICommand SendLoginRequestCommand { get; set; }

    private void SendLoginRequest()
    {
      LoginResponse response = UserServiceProxy.Login(new LoginRequest { UserName = UserName, Password = Password });
        ConsoleLog.Document += $"{response.IsSuccess} {response.Message}";
      if(response.IsSuccess == true)
        {
            AuthenticatedUser.Authentication = response.Authentication;
            JoinServiceResponse responseFromChatService = ChatServiceProxy.JoinService(new JoinServiceRequest());
            ConsoleLog.Document += responseFromChatService.Message;

            /* This is where I think the view should be changed,yet no success for a few days now.
             * 
             * 
             * 
             * 
             * 
             */
        }

    }

    private void LoginEventRaised(object sender, OnLoginEventArgs e)
    {
        ConsoleLog.Document += $"{e.UserName} has logged in.";
    }
}

SignUpViewModel.cs:

    public class SignUpViewModel : ViewModelBase
{
    public string UserName { get; set; }
    public string Password { get; set; }
    public string PasswordConfirm { get; set; }
    public ConsoleLog ConsoleLog { get; set; }
    public UserServiceProxy UserServiceProxy { get; set; }

    public ICommand OnClickSignUpCommand { get; set; }

    public SignUpViewModel()
    {
        UserServiceProxy = new UserServiceProxy();
        ConsoleLog = new ConsoleLog { Document = "Check Register."};
        OnClickSignUpCommand = new MyCommand(SendSignUpRequest);
    }

    private void SendSignUpRequest()
    {
      SignUpResponse response = UserServiceProxy.SignUp(new SignUpRequest { UserName = UserName, Password = Password, PasswordConfirm = PasswordConfirm });
        if(response.IsSuccess == true)
        {
            ConsoleLog.Document += $"{response.IsSuccess} {response.Message}";
            response.AllOtherUsers.ForEach(u => ConsoleLog.Document += $"{u.UserName} Signed up.");
        }
    }
}

ViewModelBase.cs:

    public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public virtual void Notify([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

AppViewModel.cs:

    public class AppViewModel : ViewModelBase
{
    private ViewModelBase currentView;

    public ViewModelBase CurrentView
    {
        get { return currentView; }
        set {
            currentView = value;
            Notify();
        }
    }

    public ICommand ViewLoginCommand { get; }
    public ICommand ViewSignUpCommand { get; }

    public AppViewModel()
    {
        ViewLoginCommand = new MyCommand(SetCurrentViewToLoginViewModel);
        ViewSignUpCommand = new MyCommand(SetCurrentViewToSignUpViewModel);
        CurrentView = new LoginViewModel(); //temporary loading the first view the use will see.
    }
    private void SetCurrentViewToLoginViewModel()
    {
        CurrentView = new LoginViewModel();
    }
    public void SetCurrentViewToSignUpViewModel()
    {
        CurrentView = new SignUpViewModel();
    }
}

LoginView.xaml(这是一个用户控件):

    <Grid>
    <Button x:Name="login" Content="login" HorizontalAlignment="Left" Margin="292,171,0,0" VerticalAlignment="Top" Width="114" Height="33" Command="{Binding SendLoginRequestCommand}"/>
    <TextBox x:Name="passwordTextBox" HorizontalAlignment="Left" Height="34" Margin="292,103,0,0" TextWrapping="Wrap" Text="{Binding Password}" VerticalAlignment="Top" Width="141"/>
    <TextBox x:Name="userNameTextBox" HorizontalAlignment="Left" Height="34" Margin="292,51,0,0" TextWrapping="Wrap" Text="{Binding UserName}" VerticalAlignment="Top" Width="141"/>
    <TextBlock x:Name="consoleLog" HorizontalAlignment="Left" Margin="24,33,0,0" TextWrapping="Wrap" Text="{Binding Path = ConsoleLog.Document}" VerticalAlignment="Top" Height="232" Width="218" />
    <Button x:Name="logout" Content="logout" HorizontalAlignment="Left" Margin="292,232,0,0" VerticalAlignment="Top" Width="114" Height="33"/>
</Grid>

SignUpView.xaml(此代码并非真正需要此代码，但以防万一):

    <Grid>
    <TextBox x:Name="textBox" HorizontalAlignment="Left" Height="30" Margin="310,24,0,0" TextWrapping="Wrap" Text="{Binding UserName}" VerticalAlignment="Top" Width="130"/>
    <TextBox x:Name="textBox1" HorizontalAlignment="Left" Height="30" Margin="310,74,0,0" TextWrapping="Wrap" Text="{Binding Password}" VerticalAlignment="Top" Width="130"/>
    <TextBox x:Name="textBox2" HorizontalAlignment="Left" Height="30" Margin="310,124,0,0" TextWrapping="Wrap" Text="{Binding PasswordConfirm}" VerticalAlignment="Top" Width="130"/>
    <Button x:Name="register" Content="Register" HorizontalAlignment="Left" Margin="310,176,0,0" VerticalAlignment="Top" Width="130" Command="{Binding OnClickSignUpCommand}"/>
    <TextBlock x:Name="textBlock" HorizontalAlignment="Left" Margin="25,10,0,0" TextWrapping="Wrap" Text="{Binding  Path=ConsoleLog.Document}" VerticalAlignment="Top" Height="289" Width="253"/>
</Grid>

我知道我在这里想念什么。可能是因为我试图解决几天问题，所以我迷路了。

这是我的登录信息:(尚无法嵌入)

LoginView.xaml

当我按下“登录”时，需要下一个 View 加载:

SignUpView.xaml

对于这个问题，我无法提供任何代表。不过，我非常感谢您的帮助。

浏览了网络，找不到合适的问题。

Answer 1

您确实为问题提供了很多代码，请参阅此Minimal, Complete, and Verifiable code example
在发布您的问题之前。

如果我了解您要在程序中执行的操作，则AppViewModel是您的“MainNavigation”类，该类负责管理所有 View 并在它们之间进行导航。

我可以提供的一种解决方案是将一个事件添加到LoginViewModel中，该事件将在用户成功登录后引发。在AppViewModel中，您将注册到此事件并实现一个处理程序，该处理程序会将CurrentView属性更改为SignUpViewModel。
LoginViewModel.cs的附加内容将如下所示:

public class LoginViewModel : ViewModelBase
{
    ...

    public delegate void UserLoginSuccessfullyHandler();
    public event UserLoginSuccessfullyHandler UserLoginSuccessfullyEvent;

    private void SendLoginRequest()
    {
      LoginResponse response = UserServiceProxy.Login(new LoginRequest { UserName = UserName, Password = Password });
        ConsoleLog.Document += $"{response.IsSuccess} {response.Message}";
      if(response.IsSuccess == true)
        {
            AuthenticatedUser.Authentication = response.Authentication;
            JoinServiceResponse responseFromChatService = ChatServiceProxy.JoinService(new JoinServiceRequest());
            ConsoleLog.Document += responseFromChatService.Message;

            // This is where you inform the AppViewModel to change his CurrentView
            if (UserLoginSuccessfullyEvent!= null)
                UserLoginSuccessfullyEvent();
        }
    }

    ...
}

AppViewModel.cs的附加内容将如下所示:

    public class AppViewModel : ViewModelBase
{
    ...

    public AppViewModel()
    {
        var loginViewModel = new LoginViewModel();
        loginViewModel.UserLoginSuccessfullyEvent += new UserLoginSuccessfullyHandler(myUserLoginSuccessfullyHandler);
        CurrentView = loginViewModel;
    }

    private void myUserLoginSuccessfullyHandler()
    {
        CurrentView = new SignUpViewModel();
    }

    ...
}

您可以在这里看到更多有关事件的信息 Events in C#
。