windowsphone 7-空引用异常c#wp7

当我试图删除保存文件时，也会遇到同样的错误。问题是，我已经成功创建了保存文件，但错误表明当我尝试删除它们时根本没有任何保存文件。但是，他们会记录我保存了多少保存文件。如果可能的话，有人可以检查我的代码吗？我愿意发送我的应用程序。

这里抛出了nullreference异常：

加载文件.cs

private void button2_Click(object sender, RoutedEventArgs e)
    {
        ViewDiskModel model =  this.LayoutRoot.DataContext as ViewDiskModel;
        int m_iSelectedLoad = lstBox1.SelectedIndex;
        if (m_iSelectedLoad >= 0)
        {
            model.DeleteSelectedFiles.Execute(null);
        }
        MessageBox.Show("Files Successfully Deleted");
    }

以下是负责上述代码工作的代码。

添加FileModel.cs

namespace WindowsPhoneApplication1.Model
{
    public class AddFileModel : ModelBase
    {
        private string _filename;
        public string FileName
        {
            get
            {
                return this._filename;
            }
            set
            {
                this._filename = value;
                this.OnPropertyChanged("FileName");
            }
        }
        private string _filetext10;
        public string FileText10
        {
            get
            {
                return this._filetext10;
            }
            set
            {
                this._filetext10 = value;
                this.OnPropertyChanged("FileText10");
            }
        }
        private ICommand _saveFile;
        public ICommand SaveFile
        {
            get
            {
                this._saveFile = this._saveFile ?? new DelegateCommand(this.OnSaveFile);
                return this._saveFile;
            }
        }
         private ICommand _readSelectedFiles;
        public ICommand ReadSelectedFiles
        {
            get
            {
                this._readSelectedFiles = this._readSelectedFiles ?? new DelegateCommand(this.OnReadSelected);
                return this._readSelectedFiles;
            }
        }
        private void OnSaveFile()
        {
            if (!string.IsNullOrEmpty(this.FileName))
            {
                using (var store = IsolatedStorageFile.GetUserStoreForApplication())
                {
                    if (store.FileExists(FileName))
                        store.DeleteFile(FileName);
                    using(StreamWriter writer = new StreamWriter(new IsolatedStorageFileStream(FileName, FileMode.OpenOrCreate, store)))
                    {
                        writer.WriteLine(this.FileText1 + this.FileText2 + this.FileText3 + this.FileText4 + this.FileText5 + this.FileText6 + this.FileText7 + this.FileText8 + this.FileText9 + this.FileText10);
                        writer.Close();
                    }
                }
            }
        }
        private void OnReadSelected()
        {
            using (var store = IsolatedStorageFile.GetUserStoreForApplication())
            {
                if (store.FileExists(FileName))
                {
                    using (StreamReader reader = new StreamReader(new IsolatedStorageFileStream(FileName, FileMode.OpenOrCreate, store)))
                        {
                            string textData = this.FileText1 + this.FileText2 + this.FileText3 + this.FileText4 + this.FileText5 + this.FileText6 + this.FileText7 + this.FileText8 + this.FileText9 + this.FileText10;
                         textData = reader.ReadLine(); 
                        }
                }
                else
                {
                    MessageBox.Show("File not found!");
                }
            }
        }
    }
}

ViewDiskModel.cs

namespace WindowsPhoneApplication1.Model
{
    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);
        }
    }
}

ModelBase.cs

namespace WindowsPhoneApplication1.Model
{
    public class ModelBase : INotifyPropertyChanged
    {
        #region INotifyPropertyChanged Members
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventArgs eargs = new PropertyChangedEventArgs(propertyName);
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, eargs);
        }
        #endregion
    }
}

DelegateCommand.cs

namespace WindowsPhoneApplication1.Model
{
    public class DelegateCommand : ICommand
    {
        private Action command;
        public Action Command
        {
            get { return this.command; }
        }
        private Func<bool> canExecuteCommand;
        public DelegateCommand(Action cmd, Func<bool> canexecute)
        {
            this.canExecuteCommand = canexecute;
            this.command = cmd;
        }
        public DelegateCommand(Action cmd)
        {
            this.command = cmd;
        }
        #region ICommand Members
        public bool CanExecute(object parameter)
        {
            if (this.canExecuteCommand != null)
                return this.canExecuteCommand();
            return true;
        }
        public event EventHandler CanExecuteChanged;
        public void Execute(object parameter)
        {
            if (this.command != null)
                this.command();
        }
        #endregion
    }
}

编辑：（这是我在加载页面的XAML中添加的内容）

ListBox ItemsSource="｛Binding Files｝"Margin="0,42,0115"SelectionChanged="ListBox_SelectionChanged"Name="lstBox1"DataContext="{StaticResource vmDiskModel｝">列表框。项目模板>数据模板>复选框IsChecked="｛Binding IsChecked｝"Content="｛s Binding FileName｝"/>/数据模板>/列表框。项目模板>/ListBox>

ViewDiskModel model =  this.LayoutRoot.DataContext as ViewDiskModel;