How can cnotact log in with two accounts in one app?

Using a library VK.NET.

Using the Function LoginIn autorisoes.

private void LoginIn(VkApi vk, string login, string password)
{
 vk.Authorize(new ApiAuthParams
{
 ApplicationId = AppID,
 Login = Login,
 Password = password,
 Settings = Settings.All
});
 }

The problem is that after login the second account appears VkApiAuthorizationException exception(wrong username or password). In fact, the pair login the password is correct. The exception only occurs when authorizing a second account regardless of the login and password.

The whole code:

public partial class MainWindow : Window
{
 public MainWindow()
{
InitializeComponent();
}

 private vk1 VkApi = new VkApi(), vk2 = new VkApi();

 #region logins
 private void LoginIn(VkApi vk, string login, string password)
{
 vk.Authorize(new ApiAuthParams
{
 ApplicationId = 5427437,
 Login = Login,
 Password = password,
 Settings = Settings.All
});
}

 private void CheckBox1_Checked(object sender, RoutedEventArgs e)
{
 LoginIn(vk1, Login1.Text, Password1.Text);
}

 private void Button_Click(object sender, RoutedEventArgs e)
{
vk1.Status.Set("1");
vk2.Status.Set("2");
}

 private void CheckBox2_Checked(object sender, RoutedEventArgs e)
{
 LoginIn(vk2, Login2.Text, Password2.Text);
}
#endregion
 }