c# - System.Speech not recognized -

I'm using C # 2010 Express, and I want to do speech recognition would, however, when I file In the beginning, I type the following:

  system. Using Speech;   
  System. Speech  is not recognized. Just to make sure, I installed Speech SDK from Microsoft, but I did not make any difference.  
 I am using the .NET 4.0 client profile framework, which should work fine, I think.  
 What should I do to solve it? Is this a limit of C # Express?   
 
 
 You need to add the reference solution to the Explorer:  
   
 Then right-click on the reference item and select Add Reference. Make sure you're on the tab. Scroll down until you see the system that pops up in the window that pops up. Speech.  
   
 Select it and click OK Please. Now it will recognize the speech.