Module1.vb

Module Module1

    Public animals As New List(Of Animal)

    Sub Main()
        animals.Add(New Animal("A", "HEN"))
        animals.Add(New Animal("A", "BIRD"))
        animals.Add(New Animal("A", "COW"))
        animals.Add(New Animal("B", "DOG"))
        animals.Add(New Animal("B", "DUCK"))
        animals.Add(New Animal("B", "FISH"))
        animals.Add(New Animal("C", "CAT"))
        animals.Add(New Animal("C", "CHICKEN"))
        animals.Add(New Animal("C", "PIG"))
        animals.Add(New Animal("D", "GOAT"))

        Dim result2 = From a In animals
                      Group a By grp = a.Category Into Group

        For Each ani In result2
            Console.WriteLine(ani.grp)
            For Each ani2 In animals
                If ani2.Category = ani.grp Then Console.WriteLine(ani2.Type) Else Continue For
            Next
        Next
        Console.ReadKey(True)
    End Sub

End Module

Public Class Animal

    Public Category As String
    Public Type As String

    Public Sub New(cat As String, type As String)
        Category = cat
        Me.Type = type
    End Sub

End Class