Added viewmodel

imagecatalog/ViewModelBase.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ImageCatalog_2
+{
+    public class ViewModelBase : INotifyPropertyChanged
+    {
+        public event PropertyChangedEventHandler? PropertyChanged;
+        // This method is called by the Set accessor of each property.
+        // The CallerMemberName attribute that is applied to the optional propertyName
+        // parameter causes the property name of the caller to be substituted as an argument.
+        protected void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
+        {
+            if (PropertyChanged != null)
+            {
+                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+            }
+        }
+
+    }
+}