Rearrange files to shared project

src/MayShow.Shared/ViewModels/BaseViewModel.cs

@@ -0,0 +1,46 @@
+using Avalonia.Controls;
+using MayShow.Helpers;
+using MayShow.Interfaces;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace MayShow.ViewModels;
+
+class BaseViewModel : ChangeNotifier
+{
+    IChangeViewModel _viewModelChanger;
+    ITopLevelGrabber? _topLevelGrabber;
+
+    public BaseViewModel(IChangeViewModel viewModelChanger)
+    {
+        _viewModelChanger = viewModelChanger;
+        _topLevelGrabber = null;
+    }
+
+    public ITopLevelGrabber? TopLevelGrabber
+    {
+        get => _topLevelGrabber;
+        set { _topLevelGrabber = value; }
+    }
+
+    public IChangeViewModel ViewModelChanger
+    {
+        get { return _viewModelChanger; }
+        set { _viewModelChanger = value; }
+    }
+
+    #region IChangeViewModel
+
+    public void PopViewModel()
+    {
+        _viewModelChanger?.PopViewModel();
+    }
+
+    public void PushViewModel(BaseViewModel model)
+    {
+        _viewModelChanger?.PushViewModel(model);
+    }
+
+    #endregion
+}