Dictionary<string, object> items = new Dictionary<string, object>();
items.Add("a number", 1.23f);
items.Add("a point", new Point(5,6));

JsonSerializerSettings settings = new JsonSerializerSettings() { Formatting = Formatting.Indented, TypeNameHandling=TypeNameHandling.All };
var serialized = JsonConvert.SerializeObject(items, settings);

{
  "$type": "System.Collections.Generic.Dictionary`2[[System.String, mscorlib],[System.Object, mscorlib]], mscorlib",
  "a number": 1.23,
  "a point": "5,6"
}

{
  { "a number": 1.23, "$type" : "System.Float, mscorlib..." },
  { "a point": "5,6", "$type" : "System.Drawing.Point..." }
}