Longlist selector windows phone

Question

I have a Longliseselector in Xaml for windows phone 8
i'm populating it using a database
it works fine without grouping but when i group it it just shows a few empty lists

this code works

using (Database ctx = new Database(Database.ConnectionString))
        {
            ctx.CreateIfNotExists();
            var tdr = from p in ctx.Transactions
                      join c in ctx.Type on p.Type equals c.Id
                      where p.Date > DateTime.Today.AddDays(-1 * ra) && c.Type1.Equals(ty)
                      select new { Id = p.Id, amont = p.Amont, type = c.Name, des = p.Des, dated = p.Date };
            list21.ItemsSource = tdr.ToList();
        }   

But when i group it so i have jumplists it just does not work without any errors

using (Database ctx = new Database(Database.ConnectionString))
        {
            ctx.CreateIfNotExists();
            var tdr = from ii in
                          (
                              from p in ctx.Transactions
                              join c in ctx.Type on p.Type equals c.Id
                              where p.Date > DateTime.Today.AddDays(-1 * ra) && c.Type1.Equals(ty)
                              select new { Id = p.Id, amont = p.Amont, type = c.Name, des = p.Des, dated = p.Date }
                              )
                      group ii by ii.Id;

            list32.ItemsSource = tdr.ToList();
        }  

what am i doing wrong?

Answer 1

http://msdn.microsoft.com/en-us/library/windows/apps/jj244365(v=vs.105).aspx

You have missed the KeyedList... Try:

{
        ctx.CreateIfNotExists();
        var tdr = from ii in
                      (
                          from p in ctx.Transactions
                          join c in ctx.Type on p.Type equals c.Id
                          where p.Date > DateTime.Today.AddDays(-1 * ra) && c.Type1.Equals(ty)
                          select new { Id = p.Id, amont = p.Amont, type = c.Name, des = p.Des, dated = p.Date }
                          )
                  group ii by ii.Id into iii select new KeyedList<string, COLLECTIONITEM>(iii);

        list32.ItemsSource = new List<KeyedList<string, COLLECTIONITEM>>(tdr);
    } 



public class KeyedList<TKey, TItem> : List<TItem>
    {
        public TKey Key { protected set; get; }

        public KeyedList(TKey key, IEnumerable<TItem> items)
            : base(items)
        {
            Key = key;
        }

        public KeyedList(IGrouping<TKey, TItem> grouping)
            : base(grouping)
        {
            Key = grouping.Key;
        }
    }

Don't forget this in the GroupHeaderTemplate:

<TextBlock Text="{Binding Key}" />