GetFiles is incredibly slow vb.NET - vb.net

Question

I need to process a large amount of files and scour thru a group of directories and subdirectories and get the file from the found directory. This is easy using a simple directory but when scouring a thousand directories, the program slows down to a crawl. I've heard of using enumeratefiles but I'm not how to approach this. thank you.
How should I approach this?
dim Filename_to_lookfor as string
dim filePaths As String()
for i = 0 to 1000
Filename_to_lookfor = array(i)
filePaths = Directory.GetFiles(sTargetPath, sFilename_to_lookfor.ToUpper,
IO.SearchOption.AllDirectories)
if filepath.length > 0 then
'copy file using Computer.FileSystem.CopyFile()
end if
next
Thank you.

Answer 1

Another coding would be using Linq:
Sub SearchFiles(pathAndfileNames_to_lookfor() As String, sTargetPath As String)
' Call just once Directory.GetFiles():
Dim FilePaths() As String = Directory.GetFiles(sTargetPath, "*.*", IO.SearchOption.AllDirectories)
Dim lookup1 = FilePaths.ToLookup(Function(x) x.ToLower)
Dim lookup2 = pathAndfileNames_to_lookfor.ToLookup(Function(x) x.ToLower)
Dim filesInBoth = lookup1.SelectMany(Function(x) x.Take(lookup2(x.Key).Count).ToArray)
For Each file In filesInBoth
'copy file using Computer.FileSystem.CopyFile()
Console.WriteLine(file)
Next
End Sub
Calling the procedure would be as follows:
Dim file1 As String = "C:\...\file1..."
Dim file2 As String = "C:\...\file2..."
Dim pathAndfileNames_to_lookfor() As String = New String() {file1, file2}
Dim sTargetPath = "..."
SearchFiles(pathAndfileNames_to_lookfor, sTargetPath)