How can I get the value of properties in nested classes using Reflection?

I realise the question sounds similar to some others, but they don't really answer what I need. I'm trying to use Reflection to put a big "data" class which has other data classes within it and get all these values to quickly create a JSON so that every time a new piece of data is added there is no need to re-code anything.

So, basically it would look something like this:

public class A
{
    public int data1 { set; get; }
    public B b { set; get; }
}
public class B
{
    public int data2 { set; get; }
}

//main method
{
    A a = new A();
    a.data1 = 1;
    a.b = new B();
    a.b.data2 = 2;

    PropertyInfo[] propInfos = typeof(A).GetProperties();
    foreach (PropertyInfo propInfo in propInfos)
    {
        // ??
        //if (!propInfo.GetType().IsPrimitive)
        //{
        //    PropertyInfo[] propInfosForB = propInfo.GetType().GetProperties();
        //    foreach (PropertyInfo propInfoForB in propInfos)
        //    {
        //        print(propInfoForB.GetValue(propInfo, null));
        //    }
        //}
        //else
        {               
            print(propInfo.GetValue(a, null));
        }
    }
}

So basically "1" prints fine, but I can't figure out how to get "2" from B (as part of A). All I get is loads of "1" and "B" printed or errors. Hope that makes sense.

P.S: I know serialization would be a simpler solution to put all this in a JSON, but I can't use that for different reasons.