Upload of pre-existing files

.NET/Xamarin/ViewModel.cs.md

@@ -0,0 +1,35 @@
+# ViewModel.cs
+
+```cs
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Text;
+using Xamarin.Forms;
+
+namespace AppName.ViewModels
+{
+    class PageNameViewModel : INotifyPropertyChanged
+    {
+        public MainPageViewModel()
+        {
+        }
+
+        public event PropertyChangedEventHandler PropertyChanged;  // event handler to notify changes
+
+        public string field;  // needed, if substituted by ExprBody will cause infinite loop of access with the binding
+        public string Property
+        {
+            get => field;
+            set
+            {
+                field = value;
+
+                var args = new PropertyChangedEventArgs(nameof(Property));  // EVENT: let view know that the Property has changed
+                PropertyChanged?.Invoke(this, args);  // Ivoke event to notify the view
+            }
+        }
+    }
+}
+```