title: Determine the position of an element in an IQueryable
body: <p>I have a IQueryable which is ordered by some condition. 
  Now I want to know the position of a particular element in that IQueryable.
  Is there a linq expression to get that.
  Say for example there are 10 elements in the IQueryable and the 6th element matches a condition, I want to get the number 6.</p>