title: Can't access User-Control via javascript on the outer Page
body: <p>I developed my user-control with a <code>label</code> and a <code>textbox</code> (both of them are from <code>DevExpress</code>). 
  I have a page with some controls including mine and javascript block. 
  I realize that I must use
   <code>document.getElementById("&lt;%=tbPosition.ClientID %&gt;")</code> to get access for user-control. But <code>document.getElementById("&lt;%=tbPosition.ClientID %&gt;")</code> returns null.</p>
  
  <p>Here's my code:
  1) <code>Page.aspx</code> with user control</p>
  
  <pre><code>&lt;script type="text/javascript" language="javascript"&gt;
      var tb = document.getElementById("&lt;%=tbPosition.ClientID %&gt;"); // returns null
  &lt;/script&gt;
  
  &lt;head&gt;&lt;/head&gt;
  &lt;body&gt;
      &lt;rsoft:TextBoxControl ID="tbPosition" runat="server" 
        Title="Позиция" IsRequired="true" 
        ValidationMode="UnsignedInt" ClientIDMode="Static" /&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p>2) User-control 'rsoft:TextBoxControl'</p>
  
  <pre><code>&lt;table&gt;
  &lt;tr&gt;
      &lt;td class="styleFieldLabel"&gt;
          &lt;asp:Label ID="lblTitle" Text="" runat="server" Font-Bold="True" /&gt;
          &amp;nbsp;
      &lt;/td&gt;
      &lt;td class="styleFieldInput"&gt;
          &lt;dx:ASPxTextBox ID="tbValue" runat="server" Width="500px"
              ClientIDMode="Static" ClientInstanceName="tbValue"&gt;   
          &lt;ClientSideEvents TextChanged="tbValue_TextChanged" /&gt;                     
              &lt;ValidationSettings SetFocusOnError="True" Display="Dynamic" RequiredField-ErrorText="Поле обязательно для заполнения" 
                  ErrorTextPosition="Bottom" ValidateOnLeave="false" /&gt;                
          &lt;/dx:ASPxTextBox&gt;            
      &lt;/td&gt;
  &lt;/tr&gt;
  </code></pre>
  
  <p></p>
  
  <p>Does anybody know why <code>document.getElementById("&lt;%=tbPosition.TextBoxClientID %&gt;")</code> turns into <code>document.getElementById("tbPosition_tbValue")</code>, but there's an html element "tbPosition_tbValue_I" not "tbPosition_tbValue"? It occurs when i'm using DevExpress controls inside my user-control. When my control doesn't contain devexpress but usual <code>&lt;Asp:Textbox&gt;</code> I don't have this problem.</p>