title: How to know if a session has been set
body: <p>In php i used to use </p>
  
  <pre><code>session_start();
  if(isset(SESSION["user"]))
  {
     //session is set
  }
  els{
      // there is no session 
  }
  </code></pre>
  
  <p>but do i do that in asp.net? I mean. What code can tells wheather a session is set or not</p>
  
  <p>ex:
  asp.net c#</p>
  
  <pre><code>//login.aspx
  SESSION["USER"];
  
  //user_profile.aspx
  if(SESSION["USER"])// how do i validate that??
  {
  
  }
  </code></pre>