viewmodel ins wpf gepackt, build failed

DaSaSo.Wpf/ViewModel/State/Navigation/SewerMainNavigator.cs

@@ -0,0 +1,25 @@
+using DaSaSo.Wpf.ViewModel.Interface;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DaSaSo.Wpf.ViewModel.State.Navigation
+{
+    public class SewerMainNavigator : ISewerMainNavigator
+    {
+        private BaseViewModel _currentViewModel;
+        public BaseViewModel CurrentViewModel
+        {
+            get => _currentViewModel;
+            set
+            {
+                _currentViewModel?.Dispose();
+                _currentViewModel = value;
+                StateChanged?.Invoke();
+            }
+        }
+        public event Action StateChanged;
+    }
+}