c# - How to count the number of elements that match a condition with LINQ -

I have tried a lot of things but the most logical one seems to me:

 < Code> int divisor = AllMyControls.Take (p = & gt; p.IsActiveUserControlChecked == true) .ount ();   
  AllMyControls  is a collection of  UserControls , what do I need to know is how many  UserControls  is  IActive User Control Checker  The property is set to True.  
 Tell me VS What is found in:  
  The expression of Lambda can not be converted into 'int' because it is not a representative type   
 what is in my expression That's wrong?   
 
 
  int divisor = allmailontols Where (P = & gt; PIsactive User Control Checker) .count ()   
 or simply  
  int divisor = all macintrol.count (p = & Gt; PISEactive User Control Chucker);   
 Since you are getting started, the documentation will be worth noting