Setting up source code for Avalonia port.

src.4.7/HistoryItem.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace AdvancedCalculator
+{
+    public class HistoryItem
+    {
+        #region Properties
+
+        public string Input { get; set; }
+
+        public string Output { get; set; }
+
+        #endregion
+    }
+}