Can JavaScriptSerializer exclude properties with null/default values?

FYI, if you'd like to go with the easier solution, here's what I used to accomplish this using a JavaScriptConverter implementation with the JavaScriptSerializer:

private class NullPropertiesConverter: JavaScriptConverter {
 public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer) {
  throw new NotImplementedException();
 }

 public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer) {
  var jsonExample = new Dictionary<string, object >();
  foreach(var prop in obj.GetType().GetProperties()) {
   //check if decorated with ScriptIgnore attribute
   bool ignoreProp = prop.IsDefined(typeof(ScriptIgnoreAttribute), true);

   var value = prop.GetValue(obj, BindingFlags.Public, null, null, null);
   if (value != null && !ignoreProp)
    jsonExample.Add(prop.Name, value);
  }

  return jsonExample;
 }

 public override IEnumerable<Type> SupportedTypes {
  get {
   return GetType().Assembly.GetTypes();
  }
 }
}

and then to use it:

var serializer = new JavaScriptSerializer();
serializer.RegisterConverters(new JavaScriptConverter[] {
  new NullPropertiesConverter()
});
return serializer.Serialize(someObjectToSerialize);

The solution that worked for me:

The serialized class and properties would be decorated as follows:

[DataContract]
public class MyDataClass
{
  [DataMember(Name = "LabelInJson", IsRequired = false)]
  public string MyProperty { get; set; }
}

IsRequired was the key item.

The actual serialization could be done using DataContractJsonSerializer:

public static string Serialize<T>(T obj)
{
  string returnVal = "";
  try
  {
    DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
    using (MemoryStream ms = new MemoryStream())
    {
      serializer.WriteObject(ms, obj);
      returnVal = Encoding.Default.GetString(ms.ToArray());
    }
  }
  catch (Exception /*exception*/)
  {
    returnVal = "";
    //log error
  }
  return returnVal;
}