すいません、VB４しかやってないんです、VBAはやったけど（ぼそ）　チラシの裏だって立派な書き込み空間なんだからねっ！資源の有効活用なんだからねっ！とか偉そうに言ってるけど、実は色々と書き残したいだけ

Module Module2
 
    Sub Main()
 
        Dim samples As New List(Of KeyData)
        Dim rnd As New Random
 
        Dim KeysCount = rnd.Next(1, 120)
 
        Console.WriteLine("{0} 件キー", KeysCount)
 
        For x As Integer = 1 To KeysCount
            samples.Add(New KeyData With {
                                .Key1 = rnd.Next(1, 3).ToString("KeyA-000"),
                                .Key2 = rnd.Next(1, 3).ToString("KeyB-000"),
                                .Key3 = rnd.Next(1, 3).ToString("KeyC-000"),
                                .Data1 = rnd.Next(100, 500),
                                .Data2 = Now.AddDays(rnd.Next(-100, 100))
                                })
        Next
 
        Console.WriteLine("件数 : {0}", samples.Count)
        Dim wlist = (From x In samples
                     Group By x.Key1, x.Key2, x.Key3
                     Into Group
                     Select Group).Select(Function(f) f.OrderBy(Function(r) r.Data2).FirstOrDefault).ToList
 
        Console.WriteLine("グルーピング件数 : {0}", wlist.Count)
        wlist.ForEach(Sub(x)
                          Console.WriteLine("キーごとで最も過去日付のレコード : {0}", x.ToString)
                      End Sub)
 
        Console.ReadKey()
    End Sub
 
End Module
 
Public Class KeyData
 
    Property Key1 As String
    Property Key2 As String
    Property Key3 As String
 
    Property Data1 As Integer
    Property Data2 As Date
 
    Public Overrides Function ToString() As String
        Return String.Format("{0}.{1}.{2}({3}:{4})", Key1, Key2, Key3, Data1, Data2.ToString)
    End Function
 
End Class

Module Module2
 
    Sub Main()
 
        Dim samples As New List(Of KeyData)
        Dim rnd As New Random
 
        Dim KeysCount = rnd.Next(1, 120)
 
        Console.WriteLine("{0} 件キー", KeysCount)
 
        For x As Integer = 1 To KeysCount
            samples.Add(New KeyData With {
                                .Key1 = rnd.Next(1, 3).ToString("KeyA-000"),
                                .Key2 = rnd.Next(1, 3).ToString("KeyB-000"),
                                .Key3 = rnd.Next(1, 3).ToString("KeyC-000")
                                })
        Next
 
        Console.WriteLine("件数 : {0}", samples.Count)
        Console.WriteLine("重複なし件数 : {0}", samples.Distinct.Count)
 
        Console.ReadKey()
    End Sub
 
End Module
 
Public Class KeyData
    Implements IEquatable(Of KeyData)
 
    Property Key1 As String
    Property Key2 As String
    Property Key3 As String
 
    Public Function Equals1(other As KeyData) As Boolean Implements IEquatable(Of KeyData).Equals
        Return Key1 = other.Key1 _
            AndAlso Key2 = other.Key2 _
            AndAlso Key3 = other.Key3
    End Function
 
    Public Overrides Function GetHashCode() As Integer
        Return Key1.GetHashCode Xor Key2.GetHashCode Xor Key3.GetHashCode
    End Function
End Class

<Page
     x:Class="PlayAndEditForMP3.MainPage"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:local="using:PlayAndEditForMP3"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     mc:Ignorable="d">
     <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
           RenderTransformOrigin="0.498,0.111" Margin="0,5,0,0">
         <Grid.RowDefinitions>
             <RowDefinition Height="60"/>
             <RowDefinition Height="*"/>
         </Grid.RowDefinitions>

 
         <Button x:Name="button" Content="Button" Grid.Row="0"
             HorizontalAlignment="Left" Height="38"
             VerticalAlignment="Top" Width="140"
             RenderTransformOrigin="1.538,1.397" Margin="20,12,0,0"/>
         <ListView x:Name="ItemsView"  Grid.Row="1" 
                   Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
             <ListView.ItemTemplate>
                 <DataTemplate>
                     <Border Background="{ThemeResource AppBarBackgroundThemeBrush}">
                         <Grid HorizontalAlignment="Stretch" Margin="0">
                             <TextBlock Text="{Binding}" Name="Title" />
                             <TextBlock Text="{Binding}" Name="Artist" />
                         </Grid>
                     </Border>
                 </DataTemplate>
             </ListView.ItemTemplate>
             <ListView.ItemContainerStyle>
                 <Style TargetType="ListViewItem">
                     <Setter Property="HorizontalContentAlignment" Value="Stretch" />
                 </Style>
             </ListView.ItemContainerStyle>
         </ListView>

 
     </Grid>

 

</Page>

Module Module1

 
     Sub Main()

 
         Dim samples As New List(Of SampleRecord)
         Dim rnd As New Random

 
         Dim KeysCount = rnd.Next(1, 23)

 
         Console.WriteLine("{0} 件キー", KeysCount)

 
         For x As Integer = 1 To KeysCount
             For f As Integer = 1 To rnd.Next(1, 55)
                 samples.Add(New SampleRecord With {
                                     .Key1 = x.ToString("KeyA-000"),
                                     .Key2 = x.ToString("KeyB-000"),
                                     .Key3 = x.ToString("KeyC-000"),
                                     .Data1 = f.ToString("DataA-00"),
                                     .Data2 = f.ToString("DataB-00"),
                                     .Data3 = f.ToString("DataC-00")
                                     })
             Next
         Next

 
         Dim c = From x As SampleRecord In samples
                 Group x By x.Key1, x.Key2, x.Key3
                 Into Datas = Group
                 Select New Hoge With {
                     .Key1 = Key1,
                     .Key2 = Key2,
                     .Key3 = Key3,
                     .Datas = Datas.Select(Function(f)
                                               Return New DetailData With {
                                                                 .Data1 = f.Data1,
                                                                 .Data2 = f.Data2,
                                                                 .Data3 = f.Data3
                                                                }
                                           End Function).ToList
                     }

 
         c.ToList.ForEach(Function(x)
                              Console.WriteLine("{0}-{1}-{2}-{3}", x.Key1, x.Key2, x.Key3, x.Datas.Count)
                          End Function)

 
         Console.ReadKey()
     End Sub

 

End Module

 

Public Class SampleRecord
     Property Key1 As String
     Property Key2 As String
     Property Key3 As String
     Property Data1 As String
     Property Data2 As String
     Property Data3 As String

End Class

 

Public Class DetailData
     Property Data1 As String
     Property Data2 As String
     Property Data3 As String

End Class

 

Public Class Hoge
     Property Key1 As String
     Property Key2 As String
     Property Key3 As String

 
     Property Datas As List(Of DetailData)

End Class

Dim c = From x As SampleRecord In samples
                Group x By x.Key1, x.Key2, x.Key3
                Into Datas = Group
                Select New Hoge With {
                    .Key1 = Key1,
                    .Key2 = Key2,
                    .Key3 = Key3,
                    .Datas = Datas.Select(Function(f)
                                              Return New DetailData With {
                                                                .Data1 = f.Data1,
                                                                .Data2 = f.Data2,
                                                                .Data3 = f.Data3
                                                               }
                                          End Function).ToList
                    }

Public Class Hoge
  Property HogeHoge As String 
End Class