add ICanUnload

samples/Lemon.ModuleNavigation.SampleViewModel/BaseNavigationViewModel.cs

@@ -5,7 +5,7 @@
 
 namespace Lemon.ModuleNavigation.SampleViewModel;
 
-public class BaseNavigationViewModel : ReactiveObject, INavigationAware
+public class BaseNavigationViewModel : ReactiveObject, INavigationAware, ICanUnload
 {
     public virtual string Greeting => $"Welcome to {GetType().Name}[{Environment.ProcessId}][{Environment.CurrentManagedThreadId}]{Environment.NewLine}{DateTime.Now:yyyy-MM-dd HH-mm-ss.ffff}";
 

src/Lemon.ModuleNavigation.Avaloniaui/Regions/Region.cs

@@ -80,10 +80,13 @@ public virtual void ScrollIntoView(NavigationContext item)
 
             view.DataContext = navigationAware;
             navigationAware.OnNavigatedTo(context);
-            navigationAware.RequestUnload += () =>
+            if (navigationAware is ICanUnload canUnloadNavigationAware)
             {
-                DeActivate(context);
-            };
+                canUnloadNavigationAware.RequestUnload += () =>
+                {
+                    DeActivate(context);
+                };
+            }
             Current.SetData((view, navigationAware));
             context.View = view;
             ViewCache.AddOrUpdate(context, view, (key, value) => view);
@@ -137,10 +140,13 @@ private IDataTemplate CreateRegionDataTemplate()
 
                 view.DataContext = navigationAware;
                 navigationAware.OnNavigatedTo(context);
-                navigationAware.RequestUnload += () =>
+                if (navigationAware is ICanUnload canUnloadNavigationAware)
                 {
-                    DeActivate(context);
-                };
+                    canUnloadNavigationAware.RequestUnload += () =>
+                    {
+                        DeActivate(context);
+                    };
+                }
                 Current.SetData((view, navigationAware));
                 context.View = view;
                 ViewCache.AddOrUpdate(context, view, (key, value) => view);

src/Lemon.ModuleNavigation.Wpf/Regions/Region.cs

@@ -80,10 +80,13 @@ public virtual void ScrollIntoView(NavigationContext item)
 
             view.DataContext = navigationAware;
             navigationAware.OnNavigatedTo(context);
-            navigationAware.RequestUnload += () =>
+            if (navigationAware is ICanUnload canUnloadNavigationAware)
             {
-                DeActivate(context);
-            };
+                canUnloadNavigationAware.RequestUnload += () =>
+                {
+                    DeActivate(context);
+                };
+            }
             Current.SetData((view, navigationAware));
             context.View = view;
             ViewCache.AddOrUpdate(context, view, (key, value) => view);

src/Lemon.ModuleNavigation/Abstractions/ICanUnload.cs

@@ -0,0 +1,6 @@
+namespace Lemon.ModuleNavigation.Abstractions;
+
+public interface ICanUnload
+{
+    event Action? RequestUnload;
+}

src/Lemon.ModuleNavigation/Abstractions/INavigationAware.cs

@@ -2,7 +2,6 @@
 
 public interface INavigationAware
 {
-    event Action? RequestUnload;
     void OnNavigatedTo(NavigationContext navigationContext);
     bool IsNavigationTarget(NavigationContext navigationContext);
     void OnNavigatedFrom(NavigationContext navigationContext);