整理整理

AIStudio.Wpf.DiagramDesigner.Additionals/Commands/PropertyObserverNode.cs

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+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace AIStudio.Wpf.DiagramDesigner.Additionals.Commands
+{
+    /// <summary>
+    /// Represents each node of nested properties expression and takes care of 
+    /// subscribing/unsubscribing INotifyPropertyChanged.PropertyChanged listeners on it.
+    /// </summary>
+    internal class PropertyObserverNode
+    {
+        private readonly Action _action;
+        private INotifyPropertyChanged _inpcObject;
+
+        public PropertyInfo PropertyInfo { get; }
+        public PropertyObserverNode Next { get; set; }
+
+        public PropertyObserverNode(PropertyInfo propertyInfo, Action action)
+        {
+            PropertyInfo = propertyInfo ?? throw new ArgumentNullException(nameof(propertyInfo));
+            _action = () =>
+            {
+                action?.Invoke();
+                if (Next == null) return;
+                Next.UnsubscribeListener();
+                GenerateNextNode();
+            };
+        }
+
+        public void SubscribeListenerFor(INotifyPropertyChanged inpcObject)
+        {
+            _inpcObject = inpcObject;
+            _inpcObject.PropertyChanged += OnPropertyChanged;
+
+            if (Next != null) GenerateNextNode();
+        }
+
+        private void GenerateNextNode()
+        {
+            var nextProperty = PropertyInfo.GetValue(_inpcObject);
+            if (nextProperty == null) return;
+            if (!(nextProperty is INotifyPropertyChanged nextInpcObject))
+                throw new InvalidOperationException("Trying to subscribe PropertyChanged listener in object that " +
+                                                    $"owns '{Next.PropertyInfo.Name}' property, but the object does not implements INotifyPropertyChanged.");
+
+            Next.SubscribeListenerFor(nextInpcObject);
+        }
+
+        private void UnsubscribeListener()
+        {
+            if (_inpcObject != null)
+                _inpcObject.PropertyChanged -= OnPropertyChanged;
+
+            Next?.UnsubscribeListener();
+        }
+
+        private void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
+        {
+            if (e?.PropertyName == PropertyInfo.Name || string.IsNullOrEmpty(e?.PropertyName))
+            {
+                _action?.Invoke();
+            }
+        }
+    }
+}