title: WPF change visibility based on Items in Observable-Collection
body: <p>I have the Following Collection:
  ObservableCollection&lt;CheckedFileObject&gt;  Files</p>
  <p>A CheckedFileObject contains a FileObject and a bool isChecked.
  Now when a user selects a File the isChecked Value of this file gets changed to true.</p>
  <p>If at least one CheckedFileObject contains IsChecked = true, i want to make the Delete Button Visible.</p>
  <p>So my Question is, is it possible to toggle the visibility based on an item in an ObservableCollection and how? I doesn't matter how many items there are, but if one is checked the button should be visible.</p>
  <p>Maybe something like:</p>
  <pre class="lang-xml prettyprint-override"><code> Visibility=&quot;{Binding Files[i].IsChecked, Mode=OneWay, Converter={StaticResource BooleanAndToVisibilityConverter}}&quot;
  </code></pre>
  <p>Or perhaps binding binding the ObservablCollection to a bool in the viewmodel which gets updated through something like this:</p>
  <pre class="lang-cs prettyprint-override"><code>var isVisible = Files.Any(x =&gt; x.IsChecked == true);
  </code></pre>
  <p>when the collection changes. Is this even possible?</p>