The Name Navigation does not exists

Hi,

I just encountered a strange error message. I try to Push a New Page on the Navigationstack from one of my ViewModels, but the Compiler tells me, that Navigation does not exist. Here is my File:

{
using System;
using System.IO;

using Xamarin.Forms;
using BREADy;
using BREADy.Views;

namespace BREADy.ViewModels
{

public class GalleryViewModelIngredients : GalleryViewModel {

    public void AddNewIngredient() {
    }

    protected override void AddEntry()
    {
        IngredientViewModel viewModel = new IngredientViewModel(true);

        Navigation.PushAsync(new IngredientView(viewModel));
    }

}

}
}