Linq distinct - Count

Question

I am looking to perform a query on an example list of objects

Date     Username

01/01/2011 james
01/01/2011 jamie
01/01/2011 alex
01/01/2011 james
02/01/201         


        

Answer 1

Can be done within single GroupBy call,

  var Query = list.GroupBy(
                 (item => item.DateTime),
                 (key, elements) => new  { 
                                          key = key,
                                          count = elements
                                                  .Distinct()
                                                  .Count()
                                         }
                 );