Add project files.

Framework/Core/Extensions/IObservableExtensions.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Reflection;
+
+namespace TheXamlGuy.Framework.Core
+{
+    public static class IObservableExtensions
+    {
+        public static IDisposable WeakSubscribe<TEvent>(this IObservable<TEvent> observable, IEventAggregatorInvoker invoker, Action<TEvent> onNext)
+        {
+            MethodInfo methodInfo = onNext.Method;
+            WeakReference weakReference = new(onNext.Target);
+
+            IDisposable? subscription = null;
+            subscription = observable.Subscribe(item =>
+            {
+                if (weakReference.Target is object target)
+                {
+                    invoker.Invoke(target, item, methodInfo);
+                }
+                else
+                {
+                    subscription?.Dispose();
+                }
+            });
+
+            return subscription;
+        }
+    }
+}