Navigation service for ViewModel first navigation in Xamarin

Navigator.cs

using LiteSourceGo.ViewModels;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Xamarin.Forms;


public class Navigator
{
    static Navigator instance;
    public static Navigator Instance
    {
        get { return instance ?? (instance = new Navigator()); }
    }

    INavigation FormsNavigation
    {
        get { return Application.Current.MainPage.Navigation; }
    }

    readonly Dictionary<Type, Type> _viewModelViewDictionary = new Dictionary<Type, Type>();

    public void Register(Type viewModelType, Type viewType)
    {
        if (!_viewModelViewDictionary.ContainsKey(viewModelType))
            _viewModelViewDictionary.Add(viewModelType, viewType);
    }

    public async Task PopAsync()
    {
        await FormsNavigation.PopAsync(true);
    }

    public async Task PopModalAsync()
    {
        await FormsNavigation.PopModalAsync(true);
    }

    public async Task PopToRootAsync(bool animate)
    {
        await FormsNavigation.PopToRootAsync(animate);
    }

    public void PopTo<T>() where T : BaseViewModel
    {
        var pagesToRemove = new List<Page>();

        for (int i = FormsNavigation.NavigationStack.Count - 1; i >= 0; i--)
        {
            var currentPage = FormsNavigation.NavigationStack[i] as Page;

            if (currentPage?.BindingContext.GetType() == typeof(T))
                break;

            pagesToRemove.Add(currentPage);
        }

        foreach (var page in pagesToRemove)
            FormsNavigation.RemovePage(page);
    }

    public async Task PushAsync<T>(T viewModel) where T : BaseViewModel
    {
        var view = InstantiateView(viewModel);

        await FormsNavigation.PushAsync((Page)view);
    }

    public async Task PushModalAsync<T>(T viewModel) where T : BaseViewModel
    {
        var view = InstantiateView(viewModel);

        var nv = new NavigationPage(view);

        await FormsNavigation.PushModalAsync(nv);
    }

    Page InstantiateView<T>(T viewModel) where T : BaseViewModel
    {
        var viewModelType = viewModel.GetType();

        var view = (Page)GetViewType(viewModelType);

        view.BindingContext = viewModel;

        return view;
    }

    private object GetViewType(Type viewModelType)
    {
        Type viewType = null;

        if (_viewModelViewDictionary.ContainsKey(viewModelType))
        {
            viewType = _viewModelViewDictionary[viewModelType];
        }
        else
        {
            string viewTypeName = viewModelType.FullName.Replace("ViewModel", "View");
            viewType = Type.GetType(viewTypeName);

            // We don't have it already, get it now, and add it to the dictionary
            _viewModelViewDictionary.Add(viewModelType, viewType);
        }

        return Activator.CreateInstance(viewType);
    }
}