Fix BindCommand passing incorrect parameter after assigning new ViewModel to View

src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs

@@ -68,17 +68,20 @@ public IReactiveBinding<TView, TProp> BindCommand<
     {
         ArgumentExceptionHelper.ThrowIfNull(vmProperty);
         ArgumentExceptionHelper.ThrowIfNull(controlProperty);
+        ArgumentExceptionHelper.ThrowIfNull(withParameter);
 
         var vmExpression = Reflection.Rewrite(vmProperty.Body);
         var controlExpression = Reflection.Rewrite(controlProperty.Body);
+        var parameterExpression = Reflection.Rewrite(withParameter.Body);
 
         var source = Reflection.ViewModelWhenAnyValue(viewModel, view, vmExpression).Cast<TProp>();
+        var parameterObservable = Reflection.ViewModelWhenAnyValue(viewModel, view, parameterExpression).Cast<TParam>();
 
         var bindingDisposable = BindCommandInternal<TView, TProp, TParam, TControl>(
             source,
             view,
             controlExpression,
-            withParameter.ToObservable(viewModel),
+            parameterObservable,
             toEvent);
 
         return new ReactiveBinding<TView, TProp>(

src/tests/ReactiveUI.Wpf.Tests/Wpf/WpfCommandBindingImplementationTests.cs

@@ -9,6 +9,7 @@
 
 using ReactiveUI.Tests.Utilities.Logging;
 using ReactiveUI.Tests.Wpf.Mocks;
+using ReactiveUI.Tests.Xaml.Mocks;
 
 namespace ReactiveUI.Tests.Wpf;
 
@@ -272,4 +273,22 @@ public async Task ViewModelShouldBeGarbageCollectedWhenOverwritten()
 
         await Assert.That(weakRef.IsAlive).IsFalse();
     }
+
+    [Test]
+    public async Task CommandParameterIsCorrectAfterViewModelReassignment()
+    {
+        var vm = new CommandBindingViewModel { Value = 1 };
+        var view = new CommandBindingView { ViewModel = vm };
+
+        var received = 0;
+        view.ViewModel.Command1 = ReactiveCommand.Create<int, int>(i => received = i);
+
+        var binding = new CommandBinderImplementation().BindCommand(vm, view, vm => vm.Command1, v => v.Command1, vm => vm.Value, nameof(CustomClickButton.CustomClick));
+
+        view.ViewModel = new CommandBindingViewModel { Value = 2 };
+
+        view.Command1.RaiseCustomClick();
+
+        await Assert.That(received).IsEqualTo(2);
+    }
 }