How to Group by using LINQ in VB.NET?

Question

The following code can find duplicate files based on the same file size. But I want to dynamically increase more search conditions. For example, when the variable compareName = true, add the condition that compare the file name (New FileInfo(myFile).Name); when the variable compareCreationTime = true, add the condition that compare the Creation time (New FileInfo(myFile).CreationTime).
How to do it? Thank you.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    Dim path As String = "C:\test"

    Dim files As New List(Of String)
    files.AddRange(FileIO.FileSystem.GetFiles(path, FileIO.SearchOption.SearchAllSubDirectories))

    Dim myQuery = From myFile In files
                  Group New FileInfo(myFile).FullName By myFileInfo = New FileInfo(myFile).Length
                  Into myDuplicatesGroup = Group
                  Where (myDuplicatesGroup.Count() > 1)


    Me.ListBox1.Items.Clear()

    For Each myFileGroup In myQuery
        Me.ListBox1.Items.Add("The dup. files:")
        For Each MyFile In myFileGroup.myDuplicatesGroup
            Me.ListBox1.Items.Add(MyFile)
        Next
        Me.ListBox1.Items.Add(" ")
    Next
End Sub

Answer 1

You can find several lists by each condition, then combine the results. If you want the intersection (not union), then try something like this:

Dim files As List(Of FileInfo)

files = (From p In FileIO.FileSystem.GetFiles(path, FileIO.SearchOption.SearchAllSubDirectories)
            Select New FileInfo(p)).ToList

Dim results As IEnumerable(Of FileInfo) = files

If compareLength Then
    Dim byLength = From fi In files
                    Group By fi.Length Into g = Group
                    Where g.Count() > 1
                    From i In g
                    Select i
    results = byLength
End If

If compareName Then
    Dim byName = From fi In files
                    Group By fi.Name Into g = Group
                    Where g.Count() > 1
                    From i In g
                    Select i
    results = results.Intersect(byName)
End If

If compareCreationTime Then
    Dim byCreationTime = From fi In files
                            Group By fi.CreationTime Into g = Group
                            Where g.Count() > 1
                            From i In g
                            Select i
    results = results.Intersect(byCreationTime)
End If

Adjust the code related to listbox. Use a single loop for results, which consists of FileInfo.

Answer 2

You can refer to the following code to use reflection to show the dup.files in the listbox by using linq.

Public Class Form1  
  
    Dim path As String = "E:\Test"  
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
        ComboBox1.Items.Add("Length")  
        ComboBox1.Items.Add("Name")  
        ComboBox1.Items.Add("CreationTime")  
        files = (From p In FileIO.FileSystem.GetFiles(path, FileIO.SearchOption.SearchAllSubDirectories)  
                 Select New FileInfo(p)).ToList  
    End Sub  
    Public files As New List(Of FileInfo)  
  
    Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged  
  
        Dim dupfiles = files.GroupBy(Function(f) f.[GetType]().GetProperty(ComboBox1.Text).GetValue(f)).Where(Function(g) g.Count() > 1).[Select](Function(group) New With {  
            group.Key,  
            .Items = group.ToList()  
        }).ToList()  
        ListBox1.Items.Clear()  
        For Each i In dupfiles  
            ListBox1.Items.Add(i.Key)  
  
            For Each item In i.Items  
                ListBox1.Items.Add(item.FullName)  
            Next  
  
            ListBox1.Items.Add("  ")  
        Next  
    End Sub  
End Class  

Note: I can not create two files with the same createtime, so I don't test the creatime condition.

Result: