how to capture master page content controls via Linq

Hi, I have not worked with Linq, but I need to fix this piece of code. It turns out that the code above does not capture the input or div controls !
Here is the code, the problem is that the  inputControls.Count is always Zero and cannot execture any further code.
my question how can I fix the fir two list code?
and I do not know why this.Page.Form.Controls[11].Controls   // the index of 11 means
 
List inputControls = ( from Control c in this.Page.Form.Controls[11].Controls
  where c.GetType() == typeof(TextBox)
  select c ).ToList();
List divControls = ( from Control c in this.Page.Form.Controls[11].Controls
   where c.GetType() == typeof( HtmlGenericControl ) &&
   ( (HtmlGenericControl)c ).TagName == "div"
   select c ).ToList();
 
if ( inputControls.Count > 0 )
this is some code from the GUI interface
I have about 20 fields that they all have same format as this

 Positive MAT
 
 

 

any help is appreciated.
Bob