c# - LINQ to custom objects with List<Object> member -

chv1 cdd1                                               chv2 cdd2                                               chv3 cdd3                                               chv4        cdd4                                                                                                                           sortcol                                                                                                                        searchcolcount ---- -------------------------------------------------- ---- -------------------------------------------------- ---- -------------------------------------------------- ----------- ------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------ --------------   adventure cafe columbus                                 of house                                       cook                                               624         adams, donald, 4180259,                                                                                                      a, adams, donald, 4180259                                                                                                      0  adventure cafe columbus                                 of house                                       cook                                               643         conard, virgil, 4180469,                                                                                                     a, conard, virgil, 4180469                                                                                                     0  adventure cafe columbus                                 of house                                       cook                                               629         pheiffer, seth, 4180373,                                                                                                     a, pheiffer, seth, 4180373                                                                                                     0  adventure cafe columbus                                 of house                                       cook                                               645         sees, patrick, 4180474,                                                                                                      a, sees, patrick, 4180474                                                                                                      0  adventure cafe columbus                                 of house                                       cook                                               657         walter, derek, 4180508,                                                                                                      a, walter, derek, 4180508                                                                                                      0 

the above dataset db.

i trying use linq take dataset , create custom object type, based on above data structure, 1 of members of object list data type.

i found following article, wasn't working exactly, since simple string list object type: convert datatable object linq , group by giving me following error:

cannot implicitly convert type 'system.collections.generic.ienumerable' 'system.collections.generic.list'. explicit conversion exists (are missing cast?)

i have listed adaptation code above referenced article. ideally, able dynamically create multiple "folderitem" lists based on cdd2, cdd3, cdd4, etc... number of cdd columns variable, further complicated things.

this data return wcf service json.

dnfolders = row in dndatatable.asenumerable()     group row new     {         id = row.field<string>(1),         value = row.field<string>(2)      } folder     select new folder     {         id = folder.key.id,         value = folder.key.value         folderitem = section.select(r=>r.field<string>(3)).tolist()     }; 

folder class definition:

public class folder {     [datamember(name = "id", order = 1)]     public string id { get; set; }      [datamember(name = "value", order = 2)]     public string value { get; set; }      [datamember(name = "type", order = 3)]     public string type { get; set; }      [datamember(name = "sortcol", order = 4)]     public string sortcol { get; set; }      [datamember(name = "folderitems", order = 5)]     public list<folderitem> folderitems { get; set; } } 

folderitem class definition

public class folderitem {     [datamember(name = "value", order = 1)]     public string value { get; set; }      [datamember(name = "id", order = 2)]     public string id { get; set; }      [datamember(name = "type", order = 2)]     public string type { get; set; } } 

perhaps adjustments lazyberezovsky's answer

i believe error comes dnfolders varable list ? in case must .tolist() entire query

dnfolders =      (from row in dndatatable.asenumerable()     group row new     {         id = row.field<string>(1),         value = row.field<string>(2)     } g     select new folder     {         id = g.key.id,         value = g.key.value         folderitems = g.select(r => r.field<folderitems>(5) })                        .tolist()     }).tolist();