title: binding to a list of tuples
body: <p>I have a list of tuples pairing two pieces of data... I'd like to bind the list to a data grid.  For display, it works fine... but if I try and modify an entry, it says "A TwoWay or OneWayToSource binding cannot work on the read-only property 'Item1'"... presumably Tuples are immutable in .NET 4.0.  Is there an easy way to bind to pairs of data without creating a mutable tuple class of my own?</p>