title: WPF Range Slider With Readonly Limits
body: <p>I need to allow the user of my program to select two values using a slider. As in the image below, the user would grab the blue section and slide it to the left or right. Let's pretend that the <code>18 comes from a binding to LowerBound</code> and that <code>52 comes from a binding to UpperBound</code>. The distance between these will always <code>remain 52 - 18 = 34, unless changed</code> elsewhere by the user. Otherwise, if the slider is moved to the right, the two bound values will <code>never be more than or less than 34 units</code> from each other.
  How can I do this in WPF when I only have one thumb on the slider? I need something like two thumbs with the area in between them able to be selected and moved.</p>
  <p>I suppose this is like a slider with a single thumb that is the width of the distance between the two bound values. How can I do this?</p>
  <p><img src="https://i.stack.imgur.com/iHtcq.jpg" alt="range slider" /></p>