title: C++ - in DDX_Text function should a nIDC be unique?
body: <p>Let's say we have some <code>Dialog</code> and in <code>DoDataExchange</code> function we have some <code>DDX_Text</code> calls which works with some text fields.
  Let's see a prototype:</p>
  
  <pre><code>void AFXAPI DDX_Text( CDataExchange* pDX, int nIDC, CString&amp; value );
  </code></pre>
  
  <p>I'm new to Windows Dialogs and this Dynamic Data Exchange Mechanic and i haven't found answer fast enough.
  Something tells me that <code>nIDC</code> should be unique value, but in fact in real project i see that this is not always true.</p>
  
  <p>So the question is: When can we have <code>nIDC</code> a unique and when not? Should we or should not?</p>