c# - MVVM，我是否必须将每个命令保留在自己的类中？

Question

我正在尝试用一个月的时间来习惯 MVVM 和 WPF。我正在尝试做一些基本的事情，但我不断遇到问题。我感觉大部分问题都是通过网上搜索解决的。但现在命令出现了问题。

1. 问:我看到他们正在使用 RelayCommand、DelegateCommand 或 SimpleCommand。像这样:

   public ICommand DeleteCommand => new SimpleCommand(DeleteProject);
   

即使我像他们一样创建了所有内容，我仍然将 => new SimpleCommand(DeleteProject); 部分用红色下划线表示。

到目前为止，我正在通过为每个命令创建命令类来解决这个问题，但这感觉不是正确的方法。

问:我也会发布整个项目，我想知道我是否做错了什么或者需要改进哪些地方。

xaml:

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="380" Width="250">
<StackPanel DataContext="{Binding Source={StaticResource gallery}}" Margin="10">
    <ListView DataContext="{Binding Source={StaticResource viewModel}}" 
              SelectedItem="{Binding SelectedGallery}"
              ItemsSource="{Binding GalleryList}"
              Height="150">

        <ListView.View>
            <GridView>
                <GridViewColumn Header="Name" Width="100" DisplayMemberBinding="{Binding Name}"/>
                <GridViewColumn Header="Path" Width="100" DisplayMemberBinding="{Binding Path}"/>
            </GridView>
        </ListView.View>
    </ListView>
    <TextBlock Text="Name" Margin="0, 10, 0, 5"/>
    <TextBox Text="{Binding Name}" />
    <TextBlock Text="Path" Margin="0, 10, 0, 5" />
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="40"/>
        </Grid.ColumnDefinitions>
        <TextBox Text="{Binding Path}" Grid.Column="0"/>
        <Button Command="{Binding Path=ShowFolderClick, Source={StaticResource viewModel}}"
                CommandParameter="{Binding}"
                Content="..." Grid.Column="1" Margin="10, 0, 0, 0"/>
    </Grid>

    <Grid Margin="0, 10, 0, 0">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

        <Button Command="{Binding Path=AddClick, Source={StaticResource viewModel}}" 
                CommandParameter="{Binding}" Content="Add" Grid.Column="0" Margin="15,0,0,0" />
        <Button Command="{Binding Path=DeleteClick, Source={StaticResource viewModel}}"
                Content="Delete" Grid.Column="2" Margin="0,0,15,0" />
    </Grid>
</StackPanel>

型号:

class Gallery : INotifyPropertyChanged
{

    private string _name;
    public string Name
    {
        get
        {
            return _name;
        }
        set
        {
            _name = value;
            OnPropertyChanged("Name");
        }
    }


    private string _path;

    public string Path
    {
        get
        {
            return _path;
        }
        set
        {
            _path = value;
            OnPropertyChanged("Path");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;


    private void OnPropertyChanged(params string[] propertyNames)
    {
        PropertyChangedEventHandler handler = PropertyChanged;

        if (handler != null)
        {
            foreach (string propertyName in propertyNames) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            handler(this, new PropertyChangedEventArgs("HasError"));
        }
    }
}

模型 View :

class GalleryViewModel : INotifyPropertyChanged
{
    public GalleryViewModel()
    {
        GalleryList = new ObservableCollection<Gallery>();
        this.ShowFolderClick = new ShowFolderDialog(this);
        this.AddClick = new AddGalleryCommand(this);
        this.DeleteClick = new DeleteGalleryCommand(this);
    }

    private ObservableCollection<Gallery> _galleryList;

    public ObservableCollection<Gallery> GalleryList
    {
        get { return _galleryList; }
        set { 
            _galleryList = value;
            OnPropertyChanged("GalleryList");
        }
    }

    private Gallery _selectedGallery;

    public Gallery SelectedGallery
    {
        get { return _selectedGallery; }
        set { 
            _selectedGallery = value;
            OnPropertyChanged("SelectedGallery");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(params string[] propertyNames)
    {
        PropertyChangedEventHandler handler = PropertyChanged;

        if (handler != null)
        {
            foreach (string propertyName in propertyNames) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            handler(this, new PropertyChangedEventArgs("HasError"));
        }
    }

    public AddGalleryCommand AddClick { get; set; }
    public void AddGalleryClick(Gallery gallery)
    {

        Gallery g = new Gallery();
        g.Name = gallery.Name;
        g.Path = gallery.Path;
        GalleryList.Add(g);

    }

    public DeleteGalleryCommand DeleteClick { get; set; }
    public void DeleteGalleryClick()
    {
        if (SelectedGallery != null)
        {
            GalleryList.Remove(SelectedGallery);
        }
    }

    public ShowFolderDialog ShowFolderClick { get; set; }
    public void ShowFolderDialogClick(Gallery gallery)
    {
        System.Windows.Forms.FolderBrowserDialog browser = new System.Windows.Forms.FolderBrowserDialog();
        string tempPath = "";

        if (browser.ShowDialog() == System.Windows.Forms.DialogResult.OK)
        {
            tempPath = browser.SelectedPath; // prints path
        }

        gallery.Path = tempPath;
    }
}

命令:

class AddGalleryCommand : ICommand
{
    public GalleryViewModel _viewModel { get; set; }

    public AddGalleryCommand(GalleryViewModel ViewModel)
    {
        this._viewModel = ViewModel;
    }

    public bool CanExecute(object parameter)
    {
        /*if (parameter == null)
            return false;*/
        return true;
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        this._viewModel.AddGalleryClick(parameter as Gallery);
    }
}

class DeleteGalleryCommand : ICommand
{
    public GalleryViewModel _viewModel { get; set; }

    public DeleteGalleryCommand(GalleryViewModel ViewModel)
    {
        this._viewModel = ViewModel;
    }
    public bool CanExecute(object parameter)
    {
        return true;
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        this._viewModel.DeleteGalleryClick();
    }
}

class ShowFolderDialog : ICommand
{
    public GalleryViewModel _viewModel { get; set; }

    public ShowFolderDialog(GalleryViewModel ViewModel)
    {
        this._viewModel = ViewModel;
    }
    public bool CanExecute(object parameter)
    {
        return true;
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        this._viewModel.ShowFolderDialogClick(parameter as Gallery);
    }
}

感谢您到目前为止的阅读，我会感激我得到的每一个建议。

Answer 1

有一些框架/库可以帮助简化命令绑定(bind)。例如，MVVMLight 具有 RelayCommand 的通用实现，只需要您创建属性并为其执行分配方法名称。

Here这是如何使用 Mvvmlight Relaycommand 的示例。