private void MainWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
AuthServiceClient authClient = new AuthServiceClient();
String sessionId = (String)App.Current.Properties[App.sessionPropertyName];
if (authClient.Logout(sessionId))
{
App.Current.Properties[App.sessionPropertyName] = null;
App.Current.Properties[App.loginPropertyName] = null;
}
}