© 2004 Microsoft Corporation. All rights reserved.

Figure 4 Intranet and Internet CAS Permissions

Figure 5 Determining an Assemby's Zone

Figure 6 Isolated Storage

  private IsolatedStorageFileStream CreateSettingsStream() {
  IsolatedStorageFile store =
    IsolatedStorageFile.GetUserStoreForDomain();

  return new IsolatedStorageFileStream("settings.txt",
    FileMode.Create, store);
}

private IsolatedStorageFileStream OpenSettingsStream() {
  IsolatedStorageFile store =
    IsolatedStorageFile.GetUserStoreForDomain();

  return new IsolatedStorageFileStream("settings.txt",
    FileMode.Open, store);
}

Figure 7 Saving Settings

  private void LoadSettings() {
  try {
    using( Stream       stream = OpenSettingsStream() )
    using( StreamReader reader = new StreamReader(stream) ) {
      Location = (Point)ReadSetting(reader, typeof(Point));
      ClientSize = (Size)ReadSetting(reader, typeof(Size));
    }
  }
  catch {
    // If there's nothing to read,
    // put the form in the center of the screen
    StartPosition = FormStartPosition.CenterScreen;
  }
}

private void SaveSettings() {
  // Restore so we don't store a zero size or location
  WindowState = FormWindowState.Normal;

  // Save the window location
  using( Stream       stream = CreateSettingsStream() )
  using( StreamWriter writer = new StreamWriter(stream) ) {
    WriteSetting(writer, Location);
    WriteSetting(writer, ClientSize);
  }
}

Figure 8 Type Conversions

  private object ReadSetting(StreamReader reader, Type type) {
  TypeConverter   converter = TypeDescriptor.GetConverter(type);
  return converter.ConvertFromString(reader.ReadLine());
}

private void WriteSetting(StreamWriter writer, object obj) {
  Type            type = obj.GetType();
  TypeConverter   converter = TypeDescriptor.GetConverter(type);
  writer.WriteLine(converter.ConvertToString(obj));
}

Figure 9 Talking to a Web Service

  WahooScoresService GetService() {
  WahooScoresService  service = new WahooScoresService();

  try {
    string appbase = AppDomain.CurrentDomain.BaseDirectory;

    // Set URL to server where this came from
    string site =
      System.Security.Policy.Site.CreateFromUrl(appbase).Name;
    service.Url = service.Url.Replace("//localhost/",
      "//" + site + "/");
  }
  catch( ArgumentException ) { }
  return service;
}

void GetHighScores() {
  // Get scores
  WahooScoresService service = GetService();
  WahooScore[] scores = service.GetScores();

  // Show high scores...
}

Figure 10 Dialog Restrictions

  SaveFileDialog dlg = new SaveFileDialog();
dlg.DefaultExt = ".txt";
dlg.Filter = "Text Files (*.txt)|*.txt|All files (*.*)|*.*";

// NOTE: Not allowed unless we have FileIOPermission
//dlg.AddExtension = true;
//dlg.FileName = "somefile.txt";

if( dlg.ShowDialog() == DialogResult.OK ) {
  // NOTE: Not allowed to call dlg.FileName
  using( Stream stream = dlg.OpenFile() )
  using( StreamWriter writer = new StreamWriter(stream) ) {
    writer.Write("...");
  }
}

Figure 11 Check Permission

  // Check permission helper
bool HavePermission(IPermission perm) {
    try { perm.Demand(); }
    catch( SecurityException ) { return false; }
    return true;
}

void SaveHighScore(string name, int score) {
  IPermission perm =
    new FileDialogPermission(FileDialogPermissionAccess.Save);

  if( !HavePermission(perm) ) {
    MessageBox.Show("Doh!");
    return;
  }
  •••
}

Figure 12 IEExec

  Usage: ieexec.exe url flags [securityZone] [domainId]
url          Assembly to launch, e.g. https://localhost/foo.exe
flags        Flags to control execution. Values that can be
             added together are:
             0:   no flags
             1:   create evidence for the zone
             2:   create evidence for the site
securityZone If evidenceFlags != 0, sets the security zone.
             Values can be {0, 1, 2, 3} for
             {MyComputer, Intranet, Trusted, Internet}
domainId     If evidenceFlags != 0, unused hex-encoded bytes.
             Use 00.