Can you explain how to use IMvxNavigationService to navigate between ViewModels

Introduction to IMvxNavigationService

`IMvxNavigationService` is an abstraction over native platform navigation, allowing you to navigate between ViewModels without worrying about the underlying Views. It provides a flexible and type-safe way to manage navigation in your application.

Basic Navigation

To navigate from one ViewModel to another, you can use the `Navigate` method provided by `IMvxNavigationService`. This method is asynchronous and type-safe, making it easy to implement navigation in your ViewModels.

csharp
public class MyViewModel : MvxViewModel
{
    private readonly IMvxNavigationService _navigationService;

    public MyViewModel(IMvxNavigationService navigationService)
    {
        _navigationService = navigationService;
    }

    public async Task NavigateToNextViewModel()
    {
        await _navigationService.Navigate();
    }
}

In this example, `NextViewModel` is the target ViewModel to which you want to navigate. MvvmCross will automatically locate the corresponding View for `NextViewModel` and display it.

Navigation with Parameters

If you need to pass data from one ViewModel to another, you can use the `Navigate` method with a parameter. The target ViewModel must implement `IMvxViewModel` or inherit from `MvxViewModel`.

csharp
public class MyViewModel : MvxViewModel
{
    private readonly IMvxNavigationService _navigationService;

    public MyViewModel(IMvxNavigationService navigationService)
    {
        _navigationService = navigationService;
    }

    public async Task NavigateToNextViewModelWithParameter(MyObject parameter)
    {
        await _navigationService.Navigate(parameter);
    }
}

public class NextViewModel : MvxViewModel
{
    private MyObject _myObject;

    public override void Prepare(MyObject parameter)
    {
        _myObject = parameter;
    }
}

In this example, `MyObject` is passed as a parameter to `NextViewModel`, which can then access it in its `Prepare` method.

Returning Results

If you need to return data from a ViewModel to the one that navigated to it, you can use `IMvxResultAwaitingViewModel` and `IMvxResultSettingViewModel`. This involves implementing interfaces in both the calling and the called ViewModels.

csharp
public class MyViewModel : MvxResultAwaitingViewModel
{
    private readonly IMvxNavigationService _navigationService;

    public MyViewModel(IMvxNavigationService navigationService, IMvxResultViewModelManager resultViewModelManager)
        : base(resultViewModelManager)
    {
        _navigationService = navigationService;
    }

    public async Task NavigateToNextViewModelAndAwaitResult(MyObject parameter)
    {
        await _navigationService.NavigateRegisteringToResult(parameter, ResultViewModelManager);
    }

    public override bool ResultSet(IMvxResultSettingViewModel viewModel, MyReturnObject result)
    {
        if (viewModel is NextViewModel)
        {
            // Handle the result
            return true;
        }
        return false;
    }
}

public class NextViewModel : MvxResultSettingViewModel
{
    private readonly IMvxNavigationService _navigationService;

    public NextViewModel(IMvxNavigationService navigationService, IMvxResultViewModelManager resultViewModelManager)
        : base(resultViewModelManager)
    {
        _navigationService = navigationService;
    }

    public async Task CloseAndReturnResult()
    {
        await _navigationService.CloseSettingResult(this, new MyReturnObject(), ResultViewModelManager);
    }
}

This setup allows `MyViewModel` to await a result from `NextViewModel` after navigating to it.

Checking Navigation Possibility

Before navigating to a ViewModel, you can check if navigation is possible using the `CanNavigate` method.

csharp
if (Mvx.IoCProvider.Resolve().CanNavigate())
{
    // Navigation is possible, proceed with navigation
}

Intercepting Navigation Events

You can also intercept navigation events such as `WillNavigate`, `DidNavigate`, `WillClose`, and `DidClose` by subscribing to these events on the `IMvxNavigationService`.

csharp
Mvx.IoCProvider.Resolve().DidNavigate += (sender, e) =>
{
    // Handle navigation event
};

This allows you to perform actions before or after navigation occurs.

In summary, `IMvxNavigationService` provides a robust and flexible way to manage navigation between ViewModels in MvvmCross applications, supporting parameter passing and result handling with ease.