c# - How to build a hierarchy with use Linq to object? -

i have list of data structures:

        public list<personal> personals()         {             return new list<personal>                 {                     new personal                         {                             id = 0,                             name = "name 0"                         },                     new personal                         {                             id = 1,                             name = "name 1",                             parentid = 0                         },                     new personal                         {                             id = 2,                             name = "name 2",                             parentid = 0                         },                     new personal                         {                             id = 3,                             name = "name 3",                             parentid = 0                         },                     new personal                         {                             id = 4,                             name = "name 4",                             parentid = 1                         },                     new personal                         {                             id = 5,                             name = "name 5",                             parentid = 1                         },                     new personal                         {                             id = 6,                             name = "name 6",                             parentid = 2                         },                     new personal                         {                             id = 7,                             name = "name 7",                             parentid = 2                         },                     new personal                         {                             id = 8,                             name = "name 8",                             parentid = 4                         },                     new personal                         {                             id = 9,                             name = "name 9",                             parentid = 4                         },                 };         } 

and want build tree:

public list<tree> trees()             {                 return new list<tree>                     {                         new tree                             {                                 id = 0,                                 name = "name 0",                                 list = new list<tree>                                     {                                         new tree                                             {                                                 id = 1,                                                 name = "name 1",                                                 list = new list<tree>                                                     {                                                         new tree                                                             {                                                                 id = 4,                                                                 name = "name 4"                                                             },                                                         new tree                                                             {                                                                 id = 5,                                                                 name = "name 5"                                                             }                                                     }                                             }                                     }                             }                     };             } 

how build tree linq object? have use doesn't work exactly, see below:

public list<tree> gettree(list<personal> list)         {             var listformat = list.select(x => new tree                 {                     id = x.id,                     name = x.name,                     parentid = x.parentid                 }).tolist();              var lookup = listformat.tolookup(f => f.parentid);             foreach (var tree in listformat)             {                 tree.list = lookup[tree.id].tolist();             }              return listformat;         } 

you should use recursion:

public void somemethod() {      // here `list`      var tree = gettree(list, 0); }  public list<tree> gettree(list<personal> list, int parent) {     return list.where(x => x.parentid == parent).select(x => new tree {         id = x.id,         name = x.name,         list = gettree(list, x.id)    }).tolist(); }