Output to JSON

JSON output is not built into Compare .NET Objects. You would need to use something like Newtonsoft Json: https://www.nuget.org/packages/Newtonsoft.Json/

Person p1 = null;
Person p2 = new Person();
ComparisonResult result = _compare.Compare(p1, p2);
string json = JsonConvert.SerializeObject(result.Differences, Formatting.Indented);