How do I set max character length of filenames? - vb.net

Question

I am currently using the following code to remove the defined special characters and white spaces from any file names within my defined directory:
For Each file As FileInfo In files
newName = Regex.Replace(file.Name, "[!##$%^&*()_ ]", "")
If (file.Name <> newName) Then
newPath = Path.Combine(dir, newName)
file.CopyTo(newPath)
End If
Next
Edit: How do I trim the characters of the new file name (newName) to all but the first 26 characters?
Answer:
For Each file As FileInfo In files
If (file.Name.Length >= 36) Then
Dim maxLen As Integer = 26 - file.Extension.Length
newName = ${Regex.Replace(Path.GetFileNameWithoutExtension(file.Name), "[!##$%^&*()_ ]",
"").Substring(0, maxLen)}{file.Extension}"
newPath = Path.Combine(dir, newName)
file.CopyTo(newPath, True)
ElseIf (file.Name.Length < 36) Then
newName = Regex.Replace(file.Name, "[!##$%^&*()_ ]", "")
If (file.Name <> newName) Then
newPath = Path.Combine(dir, newName)
file.CopyTo(newPath)
End If
End If
Next

Answer 1

You can use Linq as follows:
Dim dir = "c:\myFolder"
Dim except = "[!##$%^&*()_ ]".ToArray
For Each file As FileInfo In files
Dim maxLen As Integer = 26 - file.Extension.Length
Dim newPath = Path.Combine(dir,
$"{New String(Path.GetFileNameWithoutExtension(file.Name).
ToCharArray.
Except(except).
Take(maxLen).
ToArray)}{file.Extension}")
file.CopyTo(newPath, True)
Next
Suppose you have a file with name:
abcdefg_hijk!lm#pno#pq%r(stuvy)x$z.dbf
The newPath output will be:
c:\myFolder\abcdefghijklmpnoqrstuv.dbf
If that is what you need to do.
Edit:
Alternative using RegEx:
Dim except = "[!##$%^&*()_ ]"
For Each file As FileInfo In files
Dim maxLen As Integer = 26 - file.Extension.Length
Dim newName = $"{Regex.Replace(Path.GetFileNameWithoutExtension(file.Name),
except,
"").Substring(0, maxLen)}{file.Extension}"
Dim newPath = Path.Combine(dir, newName)
file.CopyTo(newPath, True)
Next
So the newPath for a file with name:
n_BrucesMiddle NH 12 34 5 W3_H.dbf
... will be:
c:\myFolder\nBrucesMiddleNH12345W3.dbf
The unwanted characters have been removed and the maximum length of the new file name (newName) including the extension is 26.
Here's regex101 example.
Again, if that is what you need. Good luck.

Answer 2

Use String.Remove
newName = newName.Remove(26)
Note that: string length should be greater than or equal to 26
EDIT:
If you want the extension to remain. use this instead:
newName = newName.Remove(26, newName.length - 30)

Answer 3

To rename files you can use .MoveTo method.
From the docs:
Moves a specified file to a new location, providing the option to
specify a new file name.
You probably want to rename only the "name" part so extension remain unchanged.
This approach will support any file extension (not only extension with 3 characters)
For Each file As FileInfo In files
Dim newName As String = Path.GetFileNameWithoutExtension(file.Name).Remove(26)
Dim newPath = Path.Combine(file.DirectoryName, $"{newName}{file.Extension}")
file.MoveTo(newPath)
Next

Answer 4

If you are asking how to get a subset of a String, you would get the Substring. If you want the first 26 characters it would be the second overload.
Example:
Dim filename As String = "this is a terrible f^ln#me! that is (way) too long.txt"
Dim newFilename As String = Regex.Replace(filename, "[!##$%^&*()_ ]", String.Empty).Substring(0, 26)
Live Demo: Fiddle
Update
As per your comment, here is how you'd trim down just the filename without the extension:
Dim filename As String = "this is a terrible f^ln#me! that is (way) too long.txt"
Dim extension As String = Path.GetExtension(filename)
Dim shortFilename As String = Path.GetFileNameWithoutExtension(filename)
Dim newFilename As String = Regex.Replace(shortFilename, "[!##$%^&*()_ ]", String.Empty).Substring(0, 26) & extension
Live Demo: Fiddle