support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Interactivity/NameResolver.cs

@@ -0,0 +1,124 @@
+using System;
+using System.Windows;
+
+namespace HandyControl.Interactivity
+{
+    internal sealed class NameResolver
+    {
+        private string _name;
+        private FrameworkElement _nameScopeReferenceElement;
+
+        private FrameworkElement ActualNameScopeReferenceElement
+        {
+            get
+            {
+                if (NameScopeReferenceElement != null && Interaction.IsElementLoaded(NameScopeReferenceElement))
+                    return GetActualNameScopeReference(NameScopeReferenceElement);
+                return null;
+            }
+        }
+
+        private bool HasAttempedResolve { get; set; }
+
+        public string Name
+        {
+            get =>
+                _name;
+            set
+            {
+                var oldObject = Object;
+                _name = value;
+                UpdateObjectFromName(oldObject);
+            }
+        }
+
+        public FrameworkElement NameScopeReferenceElement
+        {
+            get =>
+                _nameScopeReferenceElement;
+            set
+            {
+                var nameScopeReferenceElement = NameScopeReferenceElement;
+                _nameScopeReferenceElement = value;
+                OnNameScopeReferenceElementChanged(nameScopeReferenceElement);
+            }
+        }
+
+        public DependencyObject Object
+        {
+            get
+            {
+                if (string.IsNullOrEmpty(Name) && HasAttempedResolve)
+                    return NameScopeReferenceElement;
+                return ResolvedObject;
+            }
+        }
+
+        private bool PendingReferenceElementLoad { get; set; }
+
+        private DependencyObject ResolvedObject { get; set; }
+
+        public event EventHandler<NameResolvedEventArgs> ResolvedElementChanged;
+
+        private FrameworkElement GetActualNameScopeReference(FrameworkElement initialReferenceElement)
+        {
+            var element = initialReferenceElement;
+            if (!IsNameScope(initialReferenceElement))
+                return element;
+            return initialReferenceElement.Parent as FrameworkElement ?? element;
+        }
+
+        private bool IsNameScope(FrameworkElement frameworkElement)
+        {
+            return frameworkElement.Parent is FrameworkElement parent && parent.FindName(Name) != null;
+        }
+
+        private void OnNameScopeReferenceElementChanged(FrameworkElement oldNameScopeReference)
+        {
+            if (PendingReferenceElementLoad)
+            {
+                oldNameScopeReference.Loaded -= OnNameScopeReferenceLoaded;
+                PendingReferenceElementLoad = false;
+            }
+            HasAttempedResolve = false;
+            UpdateObjectFromName(Object);
+        }
+
+        private void OnNameScopeReferenceLoaded(object sender, RoutedEventArgs e)
+        {
+            PendingReferenceElementLoad = false;
+            NameScopeReferenceElement.Loaded -= OnNameScopeReferenceLoaded;
+            UpdateObjectFromName(Object);
+        }
+
+        private void OnObjectChanged(DependencyObject oldTarget, DependencyObject newTarget)
+        {
+            ResolvedElementChanged?.Invoke(this, new NameResolvedEventArgs(oldTarget, newTarget));
+        }
+
+        private void UpdateObjectFromName(DependencyObject oldObject)
+        {
+            DependencyObject obj2 = null;
+            ResolvedObject = null;
+            if (NameScopeReferenceElement != null)
+            {
+                if (!Interaction.IsElementLoaded(NameScopeReferenceElement))
+                {
+                    NameScopeReferenceElement.Loaded += OnNameScopeReferenceLoaded;
+                    PendingReferenceElementLoad = true;
+                    return;
+                }
+                if (!string.IsNullOrEmpty(Name))
+                {
+                    var actualNameScopeReferenceElement = ActualNameScopeReferenceElement;
+                    if (actualNameScopeReferenceElement != null)
+                        obj2 = actualNameScopeReferenceElement.FindName(Name) as DependencyObject;
+                }
+            }
+            HasAttempedResolve = true;
+            ResolvedObject = obj2;
+            if (!Equals(oldObject, Object))
+                OnObjectChanged(oldObject, Object);
+        }
+    }
+}