Best way to loop through a list within a sub-loop - vb.net

Question

First things first, I did a search before posting this question but the answers are so generic that I could not find anything similar to what I'm trying to do. I apologize in advance if this has been answered before and I did not find it.
I have a scenario where I already collected a large list of rows (>10K) from the SQL server and put into an array (List) of strings. These rows are consisted of filenames. Because I already put them on a list, I don't want to query the SQL server again and instead want work with what I already have in memory.
This is the code I'm trying to get right:
'Valid file types for InfoLink1, InfoLink2, InfoLink3
Dim lstValidImageFormats As New List(Of String)({".JPG", ".JPEG", ".JPE", ".BMP", ".PNG", ".TIF", ".TIFF", ".GIF"})
Dim lstValidSTLFormats As New List(Of String)({".STL"})
Dim lstValidSTEPFormats As New List(Of String)({".STP", ".STEP"})
'////////////////
'// Components //
'////////////////
'We don't check Parts.InfoLink because all formats are allowed in this field
'Parts.InfoLink1 - File in Infolink1 columns MUST BE images
For i = 0 To arrStrComponentsInfolink1Values.Count - 1 'We have 10K rows with filenames in this list
For Each FileExtension As String In lstValidImageFormats
If arrStrComponentsInfolink1Values.Item(i).EndsWith(FileExtension) = False Then
End If
Next
Next
I'm trying to parse each item (filename) I have in the array arrStrComponentsInfolink1Values and check if the filename DOES NOT end with one of the extensions in the list lstValidImageFormats. If it doesn't, then I'll send the filename to another list (array).
My difficulty here is about how to iterate through each item in arrStrComponentsInfolink1Values, then check if each filename ends with one of the extensions declared in lstValidImageFormats, do what I want to do with the item if it DOES NOT end with one of those extensions, and then proceed to parse the next item in arrStrComponentsInfolink1Values.
I sincerely don't know what's the best way/performance efficient to do that.
My code above is empty because algorithmically I don't know the best approach to do what I want without querying the SQL server again with something like AND filename NOT LIKE '%.JPG' AND filename NOT LIKE '%.JPEG' AND filename NOT LIKE '%.JPE' AND filename NOT LIKE '%.BMP'...
Because I already have the data in the memory in a list, performance would be much better if I could use what I already have.
Any suggestions or material I could read to learn how to do what I'm looking for?
Thank you!

Answer 1

Here's how I would tackle this:
Dim invalidFormatFiles = _
From x In arrStrComponentsInfolink1Values _
Let fi = New FileInfo(x) _
Where Not lstValidImageFormats.Contains(fi.Extension.ToUpperInvariant()) _
Select x
For Each invalidFormatFile In invalidFormatFiles
' Do your processing
Next

Answer 2

I ended up doing this and it worked:
Dim lstValidImageFormats As New List(Of String)({".JPG", ".JPEG", ".JPE", ".BMP", ".PNG", ".TIF", ".TIFF", ".GIF"})
Dim lstValidSTLFormats As New List(Of String)({".STL"})
Dim lstValidSTEPFormats As New List(Of String)({".STP", ".STEP"})
'////////////////
'// Components //
'////////////////
'We don't check Parts.InfoLink because all formats are allowed in this field
'Parts.InfoLink1 - File in Infolink1 columns MUST BE images
Dim intExtCounter As Integer = 0
For i = 0 To arrIntComponentsInfolink1UNRs.Count - 1 'We have 10K rows with filenames in this list
intExtCounter = 0
For j = 0 To lstValidImageFormats.Count - 1
If arrStrComponentsInfolink1Values.Item(i).EndsWith(lstValidImageFormats.Item(j)) = True Then
intExtCounter += 1
End If
Next
If intExtCounter = 0 Then 'At least one file extension was found
arrIntComponentsInfolink1UNRsReportSectionInvalidExtensions.Add(i) 'File extension is not in the list of allowed extensions
End If
Next
But #41686d6564 answer was the best solution:
Dim newList = arrStrComponentsInfolink1Values.Where(Function(x) Not lstValidImageFormats.Contains(IO.Path.GetExtension(x))).ToList()
Thank you!