LInq querying collection inside collection

Question

my object contains a collection of collections . i like to get all child object ids and store it in a string array.

MainObject contains List of parent

Parent contains List of Child

Child properties are (Id,Name)

how can i query MainObject and find all child ids and store it in string array using linq?

Answer 1

You can use SelectMany:

var stringArray = MainObject.ListOfParent
                            .SelectMany(p => p.ListOfChildren
                                              .Select(c => c.Id.ToString()))
                            .ToArray()

Answer 2

try this

var id =parents.SelectMany(p => p.Children).Select(x => x.Id).ToArray();