VB.net Apply function to items in a list - vb.net

Question

I have a list of string containing full file paths and I'd like to apply a function to each path in that list and get the result in the same or a new list.
Dim Remove As New List(Of String)
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Assemblies\045-0201.iam")
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Parts\212-D017.ipt")
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Parts\211-W01.iam")
Function FileName(spth As String) As String
'Returns filename with extension from full path
Return System.IO.Path.GetFileName(spth)
End Function
The end result I'd like is for the list Remove to contain the following. I know I could use a loop to do this but I've been learning about lambda expressions lately and feel there should be a simple solution to this.
{"045-0201.iam", "212-D017.ipt", "211-W01.iam"}

Answer 1

Try this
Dim Remove As New List(Of String)
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Assemblies\045-0201.iam")
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Parts\212-D017.ipt")
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Parts\211-W01.iam")
Remove = Remove.Select(Function(s)
Return IO.Path.GetFileName(s)
End Function).ToList

Answer 2

Calling Select and ToList on the existing List is most likely fine and what most people would do. It's worth being aware, though, that that will not modify the existing collection but rather return a new one. If you only have the one reference to that list then that's not a big deal but other references to the existing list will not see the change, e.g.
Dim fileNames As New List(Of String) From {"C:\Folder\File1.ext",
"C:\Folder\File2.ext",
"C:\Folder\File3.ext"}
Dim temp = fileNames
fileNames = fileNames.Select(Function(s) Path.GetFileName(s)).ToList()
For Each fileName In fileNames
Console.WriteLine(fileName)
Next
For Each fileName In temp
Console.WriteLine(fileName)
Next
If you run that then you'll see that the first loop displays just the files names but the second loop displays the full paths, because it still refers to the original list.
If that's a problem, there is another way to do this without an explicit loop:
Dim fileNames As New List(Of String) From {"C:\Folder\File1.ext",
"C:\Folder\File2.ext",
"C:\Folder\File3.ext"}
Dim temp = fileNames
Array.ForEach(Enumerable.Range(0, fileNames.Count).ToArray(),
Sub(i) fileNames(i) = Path.GetFileName(fileNames(i)))
For Each fileName In fileNames
Console.WriteLine(fileName)
Next
For Each fileName In temp
Console.WriteLine(fileName)
Next
If you run that then you'll see that both loops display just the file names because there's only one list.
That said, if the first code posed a problem because of multiple references to the list, I'd just use a loop.

Answer 3

I know you stated that you'd want something other than a loop, but there really is no needfor anything fancy here. By the way, writing Remove.Add sounds like a riddle.
Sub Main()
Dim Remove As New List(Of String)
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Assemblies\045-0201.iam")
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Parts\212-D017.ipt")
Remove.Add("C:\_Vault\Designs\Jobs\Customer\Job23\Parts\211-W01.iam")
Console.WriteLine("Before execution")
For Each s As String In Remove
Console.WriteLine(s)
Next
For i As Integer = 0 To Remove.Count - 1
Remove(i) = MyFunction(Remove(i))
Next
Console.WriteLine("After execution")
For Each s As String In Remove
Console.WriteLine(s)
Next
Console.ReadLine()
End Sub
Private Function MyFunction(path As String) As String
Return IO.Path.GetFileName(path)
End Function
This outputs: