How to know the number of subscribers

In C # I will develop an application to control views and subscribers of my channel ...

I tried to enter this code:

static long Inscritos(string youtube_addr){
var wb=new WebBrowser();
wb.Navigate(youtube_addr); // Sendo http://youtube.com/user/meu_canal/about

var countAll = wb.Document.getElementsByTagName('b')[0];
retun Convert.ToInt64(countAll);

Then when I call MessageBox.Show(Inscritos('http://youtube.com/user/malena010102/about').ToString());

The result is blank text!