private void HandleAuthenticationRequiredMessage(AuthenticationRequiredMessage msg)
 {
     var model = new CredentialsModel {PromptMessage = msg.Message};
     var credentialsDialog = new CredentialsDialog (model);
     var dialogResult = credentialsDialog.ShowDialog();
     msg.Callback(dialogResult, model.UserName, model.Password);
 }
 public CredentialsDialog(CredentialsModel viewModel)
 {
     InitializeComponent();
     _viewModel = viewModel;
     DataContext = _viewModel;
 }