WPF中模型视图和视图模型之间的关系

问题描述：

我已经使用MVVM创建了登录身份验证，并且它工作正常。这是我做了什么：WPF中模型视图和视图模型之间的关系

MainWinodw.xaml

<Window.Resources> 
    <BooleanToVisibilityConverter x:Key="BoolToVis" /> 
</Window.Resources> 
<Grid> 
    <Grid.ColumnDefinitions> 
     <ColumnDefinition /> 
     <ColumnDefinition /> 
    </Grid.ColumnDefinitions> 
    <Grid.RowDefinitions> 
     <RowDefinition Height="Auto" /> 
     <RowDefinition Height="Auto" /> 
     <RowDefinition Height="Auto" /> 
     <RowDefinition Height="Auto" /> 
    </Grid.RowDefinitions> 
    <TextBlock Grid.Row="0" Grid.Column="0">UserName:</TextBlock> 
    <TextBlock Grid.Row="1" Grid.Column="0">Password:</TextBlock> 
    <TextBox Grid.Row="0" Grid.Column="1" Text="{Binding UserName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /> 
    <TextBox Grid.Row="1" Grid.Column="1" Text="{Binding Password, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /> 
    <Label Grid.Row="3" Grid.ColumnSpan="2" Visibility="{Binding isAuthenticated, Converter={StaticResource BoolToVis}}"> 
     User has been authenticated 
    </Label> 
    <Label Grid.Row="3" Grid.ColumnSpan="2" Visibility="{Binding LoginFail, Converter={StaticResource BoolToVis}}"> 
     Please enter valid UserName and Password 
    </Label> 

    <Button Grid.Row="2" Grid.Column="1" Content="Authenticate" Command="{Binding LoginCommand}" Margin="3" Width="100" HorizontalAlignment="Right" /> 
</Grid>

UserViewModel.cs

public class LoginViewModel : INotifyPropertyChanged 
{ 
    private bool _isAuthenticated; 
    public bool isAuthenticated 
    { 
     get { return _isAuthenticated; } 
     set 
     { 
      if (value != _isAuthenticated) 
      { 
       _isAuthenticated = value; 
       OnPropertyChanged("isAuthenticated"); 
      } 
     } 
    } 

    private bool _loginFail; 
    public bool LoginFail 
    { 
     get { return _loginFail; } 
     set 
     { 
      if (value != _loginFail) 
      { 
       _loginFail = value; 
       OnPropertyChanged("LoginFail"); 
      } 
     } 
    } 

    private string _username; 
    public string UserName 
    { 
     get { return _username; } 
     set 
     { 
      _username = value; 
      OnPropertyChanged("UserName"); 
     } 
    } 

    private string _password; 
    public string Password 
    { 
     get { return _password; } 
     set 
     { 
      _password = value; 
      OnPropertyChanged("Password"); 
     } 
    } 

    public ICommand LoginCommand 
    { 
     get { return new RelayCommand(param => this.Login()); } 
    } 

    public void Login() 
    { 
     //TODO check username and password vs database here. 
     //If using membershipprovider then just call Membership.ValidateUser(UserName, Password) 
     //if (!String.IsNullOrEmpty(UserName) && !String.IsNullOrEmpty(Password)) 
     // isAuthenticated = true; 
     isAuthenticated = LoginDataLayer.AuthenticateUser(UserName, Password); 
     if(isAuthenticated == true) 
     { 
      LoginFail = false; 
     } 
     else 
     { 
      LoginFail = true; 
     } 

    } 

    #region INotifyPropertyChanged Methods 

    public void OnPropertyChanged(string propertyName) 
    { 
     this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); 
    } 

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs args) 
    { 
     if (this.PropertyChanged != null) 
     { 
      this.PropertyChanged(this, args); 
     } 
    } 


    public event PropertyChangedEventHandler PropertyChanged; 

    #endregion 
}

这是工作的罚款。但正如我所说我是MVVM的新手。我也在viewmodel中编写模型代码。意识到我的错误后，我想这样的分离模型和视图模型代码：

UserModel.cs

public class UserModel : INotifyPropertyChanged 
{ 
    private bool _isAuthenticated; 
    public bool isAuthenticated 
    { 
     get { return _isAuthenticated; } 
     set 
     { 
      if (value != _isAuthenticated) 
      { 
       _isAuthenticated = value; 
       OnPropertyChanged("isAuthenticated"); 
      } 
     } 
    } 

    private bool _loginFail; 
    public bool LoginFail 
    { 
     get { return _loginFail; } 
     set 
     { 
      if (value != _loginFail) 
      { 
       _loginFail = value; 
       OnPropertyChanged("LoginFail"); 
      } 
     } 
    } 

    private string _username; 
    public string UserName 
    { 
     get { return _username; } 
     set 
     { 
      _username = value; 
      OnPropertyChanged("UserName"); 
     } 
    } 

    private string _password; 
    public string Password 
    { 
     get { return _password; } 
     set 
     { 
      _password = value; 
      OnPropertyChanged("Password"); 
     } 
    } 

    #region INotifyPropertyChanged Methods 

    public void OnPropertyChanged(string propertyName) 
    { 
     this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); 
    } 

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs args) 
    { 
     if (this.PropertyChanged != null) 
     { 
      this.PropertyChanged(this, args); 
     } 
    } 


    public event PropertyChangedEventHandler PropertyChanged; 

    #endregion 
}

UserViewModel.cs

public void Login() 
    { 
     UserModel obj = new UserModel(); 


     obj.isAuthenticated = LoginDataLayer.AuthenticateUser(obj.UserName,obj. Password); 
     if(obj.isAuthenticated == true) 
     { 
      obj.LoginFail = false; 
     } 
     else 
     { 
      obj.LoginFail = true; 
     } 

    }

但我正在逐渐obj.username为空。那么任何人都可以帮助我如何在视图模型中获取模型属性，以及如何更新模型属性。请帮忙。谢谢

我不认为thatr你不能让你的逻辑都在一起。在ViewModel中使用方法不成问题。您可以继续使用您的方法 – Apoorv

，但我在许多网站上阅读，模型和视图模型必须是分开的。 –

确定做一件事..在您的UserViewModel.cs中替换UserModel obj = new UserModel（）与ObservableCollection coll = new ObservableCollection （）;然后尝试访问这些值并查看您是否仍然收到空值？ – Apoorv

答

正如我所看到的，您的视图datacontext是viewModel，但属性在Model上。让你的usermodel从视图模型入店，像这样：

视图模型：

private UserModel _userModel; 
public UserModel userModel 
{ 
    get { return _userModel; } 
    set 
    { 
     _userModel = value; 
     OnPropertyChanged("userModel"); 
    } 
}

查看：

<TextBox Text="{Binding userModel.UserName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

WPF中模型视图和视图模型之间的关系

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