C# and WPF tutorial files

WPF/03-TreeViewsSimpleViewModel/WpfTreeView/Directory/ViewModels/Base/BaseViewModel.cs

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+using PropertyChanged;
+using System.ComponentModel;
+
+namespace WpfTreeView
+{
+    /// <summary>
+    /// A base view model that fires Property Changed events as needed
+    /// </summary>
+    [ImplementPropertyChanged]
+    public class BaseViewModel : INotifyPropertyChanged
+    {
+        /// <summary>
+        /// The event that is fired when any child property changes its value
+        /// </summary>
+        public event PropertyChangedEventHandler PropertyChanged = (sender, e) => { };
+    }
+}