How do I turn a C object into a JSON string in NET

Question

I have classes like these:

class MyDate
{
    int year, month, day;
}

class Lad
{
    string firstName;
    string lastName;
    MyDate dateOfBirth;
}

And I would like to turn a Lad object into a JSON string like this:

{
    "firstName":"Rohit",
    "lastName":"Sharma",
    "dateOfBirth":
    {
        "year":"1901",
        "month":"4",
        "day":"30"
    }
}

I discovered this link, but.NET 4 doesn't support the namespace it uses. JSON.NET is another option I've heard about, but I don't like the idea of requiring external DLL files, and their website currently appears to be unavailable.

Exist any other choices except writing a JSON string writer by hand?