I have written the below

return  (from p in returnObject.Portfolios.ToList()
         from childData in p.ChildData.ToList()
         from retuns in p.Returns.ToList()
         select new Dictionary<DateTime, double> ()
         { p.EndDate, retuns.Value }
).ToDictionary<DateTime,double>();

Getting error

No overload for method 'Add' takes '1' arguments

Where I am making the mistake

I am using C#3.0

Thanks