Imports System

Imports System.Collections.Generic

Imports System.Linq

Public Module Module1

    Public Sub Main()

        Dim myList as List(Of myObject) = New List(Of myObject)

        'Add arbitrary values (demo only)

        myList.AddRange({New myObject("A", "B", "C", "D"), New myObject("A", "C", "D", "E"), New myObject("B", "C", "D", "E"), New myObject("C", "D", "E", "F")})

​

        'Get all objects where Prop1 is the same

        Dim duplicateProp1 = (From o As myObject in myList Group By Prop1 = o.Prop1 Into g = Group Where g.Count > 1 Select g.FirstOrDefault())

​

        'Print all the duplicate objects (demo only)

        For Each d As myObject In duplicateProp1

            Console.WriteLine(d.Prop1)

        Next

    End Sub

End Module

​

Public Class myObject

    Private _prop1 As String

    Private _prop2 As String

    Private _prop3 As String

    Private _prop4 As String

​

​

    Public Sub New(ByVal val1 As String _

           , ByVal val2 As String _

           , ByVal val3 As String _

           , ByVal val4 As String)

    _prop1 = val1

    _prop2 = val2

    _prop3 = val3

    _prop4 = val4

    End Sub

​

    Public Property Prop1() As String

    Get

        Return _prop1

    End Get

    Set(ByVal value As String)

        _prop1 = value

    End Set

    End Property

​

    Public Property Prop2() As String

    Get

        Return _prop2

    End Get

    Set(ByVal value As String)

        _prop2 = value

    End Set

    End Property

​

    Public Property Prop3() As String

    Get

        Return _prop3

    End Get

    Set(ByVal value As String)

        _prop3 = value

    End Set

    End Property

​

    Public Property Prop4() As String

    Get

        Return _prop4

    End Get

    Set(ByVal value As String)

        _prop4 = value

    End Set

    End Property

End Class