JSON Serialization Using C# 3.0 Extension Methods

I had just been playing around with C# 3.0 extension methods when Scott Hanselman posted this article about easy JSON object serialization in Ruby.  That got me thinking that with .NET Reflection and C# 3.0 extension methods, this should be easy to do in C#.  Here is what I came up with:

using System;
using System.Text;
using System.Reflection;

namespace KeithHill.CSharpExtensionMethodSample {
  public class Person {
    public string firstName = "Scott";
    public string lastName = "Hanselman";
    public DateTime birthDay = DateTime.Parse("1:1:0 1/15/1970");
    public decimal moneyInPocket = 4.5M;
  }

  class Program {
    static void Main(string[] args) {
      Person person = new Person();
      Console.WriteLine(person.ToJavaScriptObjectNotation());
    }
  }

  public static class JsonExtension {
    public static string ToJavaScriptObjectNotation(this object obj) {
      var strBld = new StringBuilder("{");
      Type objType = obj.GetType();
      bool firstIter = true;
      foreach (FieldInfo fieldInfo in 
             objType.GetFields(BindingFlags.Public | BindingFlags.Instance)) {
        if (!firstIter) strBld.Append(", ");
        strBld.AppendFormat("\"{0}\":{1}", fieldInfo.Name, 
                            GetJsonStringForFieldValue(fieldInfo, obj));
        firstIter = false;
      }
      strBld.Append("}");
      return strBld.ToString();
    } 

    private static string GetJsonStringForFieldValue(FieldInfo field, object obj) {
      string val;
      string typeName = field.FieldType.FullName;
      switch (typeName) {
        case "System.DateTime":
          TimeSpan ts = (DateTime)field.GetValue(obj) - DateTime.Parse("1/1/1970");
          val = " new Date(" + ts.TotalMilliseconds.ToString() + ")";
          break; 

        case "System.String":
          val = "\"" + (string)field.GetValue(obj) + "\"";
          break; 

        default:
          val = field.GetValue(obj).ToString();
          break;
      }
      return val;
    }
  }
} 

Now this is by no means bullet proof.  Heck I only spent about 15 minutes on it and most of that time was figuring out how the heck to convert a .NET DateTime to a JavaScript Date value.  Anyway the output looks like this:

 

{"firstName":"Scott", "lastName":"Hanselman",
 "birthDay": new Date(1213260000), "moneyInPocket":4.5}