Question

I have the following code

 Public Function ListDirLatest(ByVal Dir As String, ByVal Amount As Integer) As DataTable        
    Dim dt As DataTable = ListDir(Dir)
    If (dt Is Nothing) Then
        Return Nothing
    Else
        Return dt ' This is where i would like to implement the latest x-files logic
    End If
End Function

Private Function ListDir(ByVal Dir As String) As DataTable
    If Directory.Exists(Dir) Then
        Dim dt As DataTable = GetDT()
        Dim dirinfo As New DirectoryInfo(Dir)
        For Each fsi As FileSystemInfo In dirinfo.GetFileSystemInfos(".txt")
            Dim dr As DataRow = dt.NewRow()
            dr("FileName") = fsi.Name()
            dr("FileDate") = fsi.CreationTime()
        Next
        Return dt
    Else
        Return Nothing
    End If
End Function

Private Function GetDT() As DataTable
    'Create DataTable to hold results
    Dim dt As New DataTable("DirList")
    Dim st As System.Type = System.Type.GetType("System.String")
    dt.Columns.Add("FileName", st)
    dt.Columns.Add("FileDate", st)
    Return dt
End Function

At the moment the ListDirLatest Function will return all the files the in the directory.
How do I change the code so that it only returns the latest ‘x’ files, as specified by the Amount argument.

To Clarify I want to return the LATEST ‘x’ files in the directory.

Answer 1

You can solve your problem with a little of Linq and a the reference to System.Data.DataSetExtensions
( http://msdn.microsoft.com/en-us/library/system.data.datatableextensions(v=vs.100).aspx )

Public Function ListDirLatest(ByVal Dir As String, ByVal Amount As Integer) As DataTable        
    Dim dt As DataTable = ListDir(Dir)
    If (dt Is Nothing) Then
        Return Nothing
    Else
        Dim r = from myRow in dt.AsEnumerable()
                Order By("FileDate DESC")
                Take(Amount)
        dt = r.CopyToDataTable()
        return dt
    End If
End Function

Also, the ListDir function has a couple of errors

• Add the row information to the DataTable returned

• Use a correct pattern for GetFileSystemInfos

  Function ListDir(ByVal Dir As String) As DataTable
      If Directory.Exists(Dir) Then
          Dim dt As DataTable = GetDT()
          Dim dirinfo As New DirectoryInfo(Dir)
          For Each fsi As FileSystemInfo In dirinfo.GetFileSystemInfos("*.txt")
              Dim dr As DataRow = dt.NewRow()
              dr("FileName") = fsi.Name()
              dr("FileDate") = fsi.CreationTime()
              dt.Rows.Add(dr)
          Next
          Return dt
      Else
          Return Nothing
      End If
  End Function