LoginViewModel.cs

public class LoginViewModel : ObservableRecipient
{
	private LoginLogic _loginLogic = new LoginLogic();
	private LoginModel _loginModel = new LoginModel();

	public ICommand LoginCommand { get; set; }

	public LoginModel LoginData
	{
	    get => _loginModel;
	    set
	    {
	        SetProperty(ref _loginModel, value);
	    }
	}

	public LoginViewModel()
	{
	    LoginCommand = new RelayCommand(
	        () => Login(LoginData)
	    );
	}

	private void Login(LoginModel loginData)
	{
	    var response = _loginLogic.Login(loginData.Username, loginData.Password);
	}
}