title: How to get clientID if textbox name is in string variable
body: <p>I have written below code to check for blank value in my textbox but its generating compilation Error, please provide me solution.</p>
  
  <p>my code in javascript:</p>
  
  <pre><code> function checkTextboxNotFilled(txtbox) {
          var txtb = document.getElementById("&lt;%= " + txtbox + ".ClientID %&gt;");
          if (GetFormattedString(txtb.value) == "") {
              return true ;
          }
          else {
              return false ;
          }
      }
  </code></pre>
  
  <p>error:</p>
  
  <pre><code>'string' does not contain a definition for 'ClientID' and no extension method 'ClientID' accepting a first argument of type 'string' could be found (are you missing a using directive or an assembly reference?)
  </code></pre>
  
  <p>I am calling it like this : checkTextboxNotFilled("MytextboxName")</p>