Question

I have a nested ObservableCollection<Student>, from which how can I get a particular student based on Id value using LINQ or Lambda ? Here is my Student class:

public class Student
    {

        public Student()
        {

        }

        public string Name;
        public int ID;
        public ObservableCollection<Student> StudLists;
    }

So each student object can have again student collections and it can go like any number of nested levels. how we can do it LINQ or using Lambda ? I have tried with

var studs = StudCollections.Where(c => c.StudLists.Any(m => m.ID == 122));

But this is not giving exact Student item ? Any idea ?

Answer 1

If you mean you want to search all descendants of StudCollections, then you could write an extension method like so:

static public class LinqExtensions
{
  static public IEnumerable<T> Descendants<T>(this IEnumerable<T> source, Func<T, IEnumerable<T>> DescendBy)
  {
    foreach (T value in source)
    {
        yield return value;

        foreach (T child in DescendBy(value).Descendants<T>(DescendBy))
        {
            yield return child;
        }
    }
  }
}

and use it like so:

var students = StudCollections.Descendants(s => s.StudLists).Where(s => s.ID == 122);

If you want one student with a matching id, use:

var student = StudCollections.Descendants(s => s.StudLists).FirstOrDefault(s => s.ID == 122);

if (student != null)
{
  // access student info here
}