support for .NET framework 3.5

Still have bugs

Net35/HandyControlDemo_Net35/Data/GlobalData.cs

@@ -0,0 +1,37 @@
+using System;
+using System.IO;
+using Newtonsoft.Json;
+
+namespace HandyControlDemo.Data
+{
+    internal class GlobalData
+    {
+        public static void Init()
+        {
+            if (File.Exists(AppConfig.SavePath))
+            {
+                try
+                {
+                    var json = File.ReadAllText(AppConfig.SavePath);
+                    Config = JsonConvert.DeserializeObject<AppConfig>(json);
+                }
+                catch
+                {
+                    Config = new AppConfig();
+                }
+            }
+            else
+            {
+                Config = new AppConfig();
+            }
+        }
+
+        public static void Save()
+        {
+            var json = JsonConvert.SerializeObject(Config);
+            File.WriteAllText(AppConfig.SavePath, json);
+        }
+
+        public static AppConfig Config { get; set; }
+    }
+}