IEnumerable Items Count

Question

Hey all,
The below code:

Dim MyFiles As System.Collections.Generic.IEnumerable(Of String)
MyFiles = Directory.EnumerateFiles(MyPath, "*.txt", SearchOption.AllDirectories)
For Each MyFile As String In MyFiles
...

How to get the number of files in MyFiles?
Since it is enumerating the collection before the whole collection is returned, not possible right?
I'm more comfortable with DirectoryInfo.GetFiles, and my files are not more than 5000, so much difference in efficiency?
Thanks

Answer 1

If in your code you are using GetEnumerator in tangent with MoveNext you can not get a count.

You could run the code below prior to your code to get a count.. In my test I asked for a file count in a folder with 125,000 files for only one file extension which comes back with 12,000 plus in a count which took 2.5 seconds. So for you to traverse 5,000 files will take no time.

Imports System.IO
Public Class Form1
    Public Async Function FileCount(sender As String, allowedExtensions() As String) As Task(Of Integer)
        Return Await Task.Run(
            Function()
                Return Task.FromResult(
                    Directory.EnumerateFiles(
                        sender, 
                        "*.*", 
                        SearchOption.AllDirectories).Count(
                            Function (file)
                                Return allowedExtensions.Contains(Path.GetExtension(file))
                            End Function))
            End Function)
    End Function

    Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim watch As Stopwatch = Stopwatch.StartNew()
        Dim count = Await FileCount(MyPath, { ".txt" })
        watch.Stop()
        Dim ts As TimeSpan = TimeSpan.FromMilliseconds(watch.Elapsed.TotalMilliseconds)

        MessageBox.Show($"File count: {count,-10}{ts.TotalSeconds}")

    End Sub
End Class