parent does not update after using InsertChildAfter

[joodies]

Hello,

I tried some code in the NRefractor demo project,
I modify the syntax tree, add 2 nodes

vc.InsertChildBefore(vc.Children.Last(), AstType.Create("int b = 78;"), new Role<AstType>("Variable", AstType.Null));

vc.InsertChildBefore(vc.Children.Last(), AstType.Create(Environment.NewLine), new Role<AstType>("NewLine", AstType.Null));             

And can see the new nodes in watch window as follow,
As you can see , the new node is not there when i try syntaxtree.ToString()

source code

using System;
using System.Linq;
class Test
{
    public void Main(string[] args)
    {
         int a = 80;
    }
}

what i want as result

using System;
using System.Linq;
class Test
{
    public void Main(string[] args)
    {
         int a = 80;
         int b = 78;
    }
}