c# - 如何处理 MVVM 模式中的多个复选框？

Question

在 WPF 中绑定(bind)复选框是一个常见问题，但我仍然没有找到适合初学者的示例代码。我在 WPF 中有复选框列表来选择最喜欢的运动名称。在我的例子中，复选框的数量是静态的。谁能告诉我如何针对这个问题实现 ViewModel？

FavoriteSportsView.xaml:

  <StackPanel Height="50" HorizontalAlignment="Left" VerticalAlignment="Top" 
  Width="150">

  <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}"  
  Command="{Binding Path=SportsResponseCommand}" 
  CommandParameter="Football" 
  Content="Football" 
  Margin="5" />

  <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}" 
  Command="{Binding Path=SportsResponseCommand}" 
  CommandParameter="Hockey" 
  Content="Hockey" 
  Margin="5" />

  <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}" 
  Command="{Binding Path=SportsResponseCommand}" 
  CommandParameter="Golf" 
  Content="Golf" 
  Margin="5" />
  </StackPanel>

FavoriteSportsViewModel.cs

  public class FavoriteSportsViewModel.cs {

    //Since I am using the same IsChecked in all check box options, I found all check 
    //boxes gets either checked or unchecked when I just check or uncheck one option.
    //How do i resolve this issue? I don't think i need seprate IsChecked for each 
    //check box option.

    private bool _isChecked;
    public bool IsChecked{
      get {
           return _isChecked;
       }

      set { if (value != _isChecked) 
             _isChecked = value;
            this.OnPropertyChanged("IsChecked");
       }
    }


    //How do i detect parameter in this method?
    private ICommand _sportsResponseCommand;
    public ICommand SportsResponseCommand
    {
        get
        {
            if (_sportsResponseCommand== null)
                _sportsResponseCommand= new
                    RelayCommand(a => DoCollectSelectedGames(), p => true);
            return _sportsResponseCommand;
        }
        set
        {
            _sportsResponseCommand= value;

        }

    }

    private void DoCollectSelectedGames(){ 
      //Here i push all selected games in an array
    }


    public abstract class ViewModelBase : INotifyPropertyChanged
    {
       public event PropertyChangedEventHandler PropertyChanged;
       public void OnPropertyChanged(string propertyName)
       {
         if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
       }
    }

  }

我不确定如何在上面的 ViewModel 中执行以下操作:1. 如何实现单一方法来处理我的所有选项？2.如何检测每个复选框以查看是否选中3. 如何使用 CommandParameter？4. 如何正确实现 SportsResponseCommand

Answer 1

您的 View 模型应如下所示:

public class MyViewModel : INotifyPropertyChanged
{
    //INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;

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

    //bindable property
    private bool _football;
    public bool Football
    {
        get { return _football; }
        set
        {
            if (value != _football)
            {
                _football = value;
                this.OnPropertyChanged("Football");
            }
        }
    }

    //... and the same for Golf and Hockey
}

然后通过设置 DataContext 属性将 View 模型与 View 相关联(这很可能在 Window 或 UserControl 代码中后面，尽管有很多方法可以实现这一点)。

最后，更新您的绑定(bind)，使其看起来像:

<CheckBox IsChecked="{Binding Football, Mode=TwoWay}"  
 Content="Football" 
 Margin="5" />

<CheckBox IsChecked="{Binding Golf, Mode=TwoWay}"   
 Content="Football" 
 Margin="5" />

作为最后的评论，您实际上不需要绑定(bind) Command 属性 - 您可以编写任何需要在 View 模型的属性 setter 中运行的代码。