如何解决空引用异常c＃wp7
| 尝试删除保存文件时出现相同的错误。问题是，我已经成功创建了保存文件，但是错误表明当我尝试删除保存文件时根本没有任何保存文件。但是，它们确实跟踪我已保存了多少个保存文件。如果可能的话，有人可以自由检查我的代码吗？我愿意发送我的应用程序。 nullreference异常在这里被抛出： LoadFile.csprivate 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\");
}
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,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!\");
}
}
}
}
}
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);
}
}
}
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
}
}
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
}
}
解决方法
在不了解您的应用程序或阅读您发布的所有代码段的情况下，我很确定您要向
button2_Click
ViewDiskModel model = this.LayoutRoot.DataContext as ViewDiskModel;
this.LayoutRoot.DataContext
ViewDiskModel
ViewDiskModel
model
null
版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 dio@foxmail.com 举报，一经查实，本站将立刻删除。
