port from perforce

intromat/Intromat/ViewModels/UndoItem.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Diagnostics;
+using System.Linq.Expressions;
+using System.Reflection;
+using Intromat.Interfaces;
+using ReactiveUI;
+
+namespace Intromat.ViewModels
+{
+    public class UndoItem<TObservable, TValue> : IUndoItem where TObservable : ReactiveObject
+    {
+        private readonly TValue _newValue;
+        private readonly TObservable _observable;
+        private readonly TValue _oldValue;
+        private readonly PropertyInfo _propertyInfo;
+
+        public UndoItem(IFile file, TObservable observable, Expression<Func<TObservable, TValue>> memberLamda, TValue oldValue, TValue newValue)
+        {
+            File = file;
+            _observable = observable;
+            _oldValue = oldValue;
+            _newValue = newValue;
+            if (memberLamda.Body is MemberExpression { Member: PropertyInfo propertyInfo }) _propertyInfo = propertyInfo;
+            Debug.Assert(_propertyInfo != null);
+        }
+
+        public IFile File { get; }
+
+        public void Redo()
+        {
+            _propertyInfo.SetValue(_observable, _newValue);
+        }
+
+        public void Undo()
+        {
+            _propertyInfo.SetValue(_observable, _oldValue);
+        }
+    }
+}