Question

我的应用程序不会删除隔离存储中加载页面上的保存文件。 delete和ViewDiskModel.cs类的代码如下：

LoadingPage.cs

private void button2_Click(object sender, RoutedEventArgs e)
    {
        ViewDiskModel model = lstBox1.DataContext as ViewDiskModel;

        int m_iSelectedLoad = lstBox1.SelectedIndex;
        if (m_iSelectedLoad >= 0)
        {
            model.DeleteSelectedFiles.Execute(null);


        }

        MessageBox.Show("Files Successfully Deleted");
    }

ViewDiskModel.cs：

 public class FileItem : ModelBase
    {

        public bool isChecked;
        public bool IsChecked
        {
            get { return this.isChecked; }
            set
            {
                this.isChecked = value;
                this.OnPropertyChanged("IsChecked");
            }
        }


        public string FileName { get; set; }
        public string FileText { get; set; }



    }

    public class ViewDiskModel : ModelBase
    {
        private IsolatedStorageFile currentStore;
        public IsolatedStorageFile Store
        {
            get
            {
                this.currentStore = this.currentStore ?? IsolatedStorageFile.GetUserStoreForApplication();
                return this.currentStore;
            }
        }

        private ObservableCollection<FileItem> _files;
        public ObservableCollection<FileItem> Files
        {
            get
            {
                this._files = this._files ?? this.LoadFiles();
                return this._files;
            }
        }

        private ObservableCollection<FileItem> LoadFiles()
        {
            ObservableCollection<FileItem> files = new ObservableCollection<FileItem>();

            foreach (string filePath in this.Store.GetFileNames())
                files.Add(new FileItem { FileName = filePath });
            return files;
        }

        private ICommand _deleteSelectedFiles;
        public ICommand DeleteSelectedFiles
        {
            get
            {
                this._deleteSelectedFiles = this._deleteSelectedFiles ?? new DelegateCommand(this.OnDeleteSelected);
                return this._deleteSelectedFiles;
            }
        }

        private ICommand _readSelectedFiles;
        public ICommand ReadSelectedFiles
        {
            get
            {
                this._readSelectedFiles = this._readSelectedFiles ?? new DelegateCommand(this.OnReadSelected);
                return this._readSelectedFiles;
            }
        }

        private void OnDeleteSelected()
        {
            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication();
            List<FileItem> removedItems = new List<FileItem>();
            foreach (var item in this.Files)
            {
                if (item.IsChecked)
                    if (storage.FileExists(item.FileName))
                    {
                        storage.DeleteFile(item.FileName);
                        removedItems.Add(item);
                    }
            }

            foreach (var item in removedItems)
                this.Files.Remove(item);
        }

        private void OnReadSelected()
        {
            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication();
            List<FileItem> removedItems = new List<FileItem>();
            foreach (var item in this.Files)
            {
                if (item.IsChecked)
                    if (storage.FileExists(item.FileName))
                    {
                        storage.DeleteFile(item.FileName);
                        removedItems.Add(item);
                    }
            }

            foreach (var item in removedItems)
                this.Files.Remove(item);
        }


    }

LoadingPage.XAML：

<!--ContentPanel - place additional content here-->
        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0" DataContext="{StaticResource vmDiskModel}">
            <Button Content="Back" Height="72" HorizontalAlignment="Left" Margin="0,530,0,0" Name="button1" VerticalAlignment="Top" Width="160" Click="button1_Click" />
            <Button Content="Delete" Height="72" HorizontalAlignment="Left" Margin="150,530,0,0" Name="button2" VerticalAlignment="Top" Width="160" Click="button2_Click" />
            <Button Content="Continue" Height="72" HorizontalAlignment="Left" Margin="296,530,0,0" Name="button3" VerticalAlignment="Top" Width="160" Click="button3_Click" />
            <TextBlock Height="30" HorizontalAlignment="Left" Margin="6,6,0,0" Name="textBlock1" Text="PLease select a save file to load." VerticalAlignment="Top" />
            <ListBox ItemsSource="{Binding Files}" Margin="0,42,0,115" SelectionChanged="ListBox_SelectionChanged" Name="lstBox1" DataContext="{StaticResource vmDiskModel}">
                <ListBox.ItemTemplate>
                    <DataTemplate >
                        <CheckBox IsChecked="{Binding IsChecked}" Content="{Binding FileName}" />
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </Grid>
    </Grid>

Answer 1

当我运行代码时，我在MainPage.xaml.cs的第33行得到一个NullReferenceException 这是因为您引用了this.LayoutRoot的DataContext但从未设置过它。实际上，您已将DataContext设置为ContentPanel 因此，第32行应为：

ViewDiskModel model = this.ContentPanel.DataContext as ViewDiskModel;

此外：
视图模型不知道在使用属性的默认OneWay绑定时已检查了哪些项目。您需要将其更改为TwoWay，以便将UI中的更改反映回视图模型。

<CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}" Content="{Binding FileName}" />

通过这两项更改，将删除所选文件。

其他问题：

一个接一个地创建多个文件似乎存在一些问题，一次只创建一个，但我没有考虑过这个问题。
在使用实现Dispose()的{{1}}时，您不是在调用using（或使用IsolatedStorageFile指令）。
代码表示即使没有选择或删除文件，它也删除了文件。
该应用尝试显示IsolatedStorage配额，但手机上不存在此概念。没有配额，这就是为什么它显示64位整数的最大值，而不管手机中磁盘的大小。
可能更多......？

ViewDiskModel.DeleteSelectedFiles.Execute（null）不会删除任何文件

1 个答案: