title: XAML binding on click
body: <p>Continuing from my <a href="https://stackoverflow.com/questions/3579866/xaml-blend-dependant-data-binding">last question</a>, I'd like to know how can I bind when a button is clicked (can this be done through pure XAML?) - or more simply, how can I do XAML-like binding through C# code?</p>
  
  <p><strong>EDIT: The previous question containing info:</strong></p>
  
  <p>I want to create a listbox that'll be bound to XPath, relative to the other listbox's currently selected item.</p>
  
  <p>It's using XmlDataProvider for the data, and the XML file looks like this:</p>
  
  <pre><code>&lt;Programs&gt;
      &lt;Program name="..."&gt;
          &lt;Step name="..."/&gt;
          &lt;Step name="..."/&gt;
      &lt;/Program&gt;
      &lt;Program name="another"&gt;
  
      ...
  
  &lt;/Programs&gt;
  </code></pre>
  
  <p>So, the "parent" listbox is listing out all the programs, while "child" shows only Steps from the current Program.
  I just need a pointer on the fact what's such type of binding called.</p>
  
  <p>Thanks in advance.</p>
  
  <p><strong>End of previous question</strong></p>
  
  <p><strong><em>The question is</em></strong> how can I do a one time bind (I <strong>do not want</strong> binding to change as soon as user clicks another listbox item) when a button called "Load" is pressed?</p>