title: WPF Bind TextBox to List<string> using variable for index
body: <p>I have a Window that displays a variable number of identical UserControls which contain (among other things) a TextBox. A single ViewModel serves both the window and the UserControls. How do I bind the UserControl's TextBox's Text property to an element of a List-of-strings in my view model when the required index is passed to the constructor of the UserControl?</p>
  
  <p>I also need Mode="TwoWay" and UpdateSourceTrigger="PropertyChanged".</p>
  
  <p>Using VS2013, .NET 4.5.2, and MVVM-Light framework.</p>
  
  <p>Thank you.</p>