Broken LINQing

gistfile1.cs

var returnShift = 
                All().Aggregate(
                    (x, y) =>
                    (x.start.Ticks - desiredStartTime.Ticks) < (y.start.Ticks - desiredStartTime.Ticks) ? x : y);



Error message:

Expression of type 'System.Collections.Generic.IEnumerable`1[ShiftyEyes.Model.Shift]' cannot be used for parameter of type 'System.Linq.IQueryable`1[ShiftyEyes.Model.Shift]' of method 'ShiftyEyes.Model.Shift Aggregate[Shift](System.Linq.IQueryable`1[ShiftyEyes.Model.Shift], System.Linq.Expressions.Expression`1[System.Func`3[ShiftyEyes.Model.Shift,ShiftyEyes.Model.Shift,ShiftyEyes.Model.Shift]])'