Feedback Editja

Create a nested group

  • Artiklu
  • 2 minuti biex taqra

The following example shows how to create nested groups in a LINQ query expression. Each group that is created according to student year or grade level is then further subdivided into groups based on the individuals' names.

Example

Note

The example in this topic uses the Student class and students list from the sample code in Query a collection of objects.

var nestedGroupsQuery =
    from student in students
    group student by student.Year into newGroup1
    from newGroup2 in (
        from student in newGroup1
        group student by student.LastName
    )
    group newGroup2 by newGroup1.Key;

// Three nested foreach loops are required to iterate
// over all elements of a grouped group. Hover the mouse
// cursor over the iteration variables to see their actual type.
foreach (var outerGroup in nestedGroupsQuery)
{
    Console.WriteLine($"DataClass.Student Level = {outerGroup.Key}");
    foreach (var innerGroup in outerGroup)
    {
        Console.WriteLine($"\tNames that begin with: {innerGroup.Key}");
        foreach (var innerGroupElement in innerGroup)
        {
            Console.WriteLine($"\t\t{innerGroupElement.LastName} {innerGroupElement.FirstName}");
        }
    }
}

/* Output:
    DataClass.Student Level = SecondYear
            Names that begin with: Adams
                    Adams Terry
            Names that begin with: Garcia
                    Garcia Hugo
            Names that begin with: Omelchenko
                    Omelchenko Svetlana
    DataClass.Student Level = ThirdYear
            Names that begin with: Fakhouri
                    Fakhouri Fadi
            Names that begin with: Garcia
                    Garcia Debra
            Names that begin with: Tucker
                    Tucker Lance
    DataClass.Student Level = FirstYear
            Names that begin with: Feng
                    Feng Hanying
            Names that begin with: Mortensen
                    Mortensen Sven
            Names that begin with: Tucker
                    Tucker Michael
    DataClass.Student Level = FourthYear
            Names that begin with: Garcia
                    Garcia Cesar
            Names that begin with: O'Donnell
                    O'Donnell Claire
            Names that begin with: Zabokritski
                    Zabokritski Eugene
 */

Note that three nested foreach loops are required to iterate over the inner elements of a nested group.

See also