title: Where to place the dependency property?
body: <p>I am confused about where I put a dependency property when building a WPF application using the MVVM pattern.  Does it go in the Model or the ViewModel?</p>
  
  <h2>Edit</h2>
  
  <p>After looking at early answers (thanks for those), I find that I am still confused, so I am giving more detail to help someone explain this to me.</p>
  
  <p>I have a class called Station.  It is used by surveyors and civil engineers to represent the length along a road.  For the most part, a Station is just a double, but it has a few decorations.  First off, the format is different.  When distance along is greater than 100 feet, we add a + symbol as another way to format it.  So 1234.56 feet down the road we might have Station 12+34.56.  (I will skip the other decorations since this one is good enough for my point.)</p>
  
  <p>Thus the logic for the special formatting lives in Station, a class in the Model.  I want a TextBox in the View to take user input of 1234.56 and coerce it to a text value of "12+34.56".  So I want a TextBox to give the user access to a value in the Model, so it needs to be a dependency property.  (That is correct, isn't it?)  But the business logic for coercing/parsing/understanding how to go back and forth between a TextBox and a Station should live in the Station class.  (Right?)</p>
  
  <p>Furthermore, I will later want to give the user the ability to set the station value by clicking on a graphical drawing of the road, including dynamically updating the value as the mouse moves and locking the value in upon issuing a data point.  (Now you see why I tried to keep this brief.)</p>
  
  <p>So is this not something that I would want to make a dependency property, especially with the dynamic data point possibly getting involved later?  If not, how do I hook a text box item to a station using MVVM?  (I really have researched this a lot before asking my question, but with no success.)</p>
  
  <ul>
  <li>Paul</li>
  </ul>