Introduction
System.IO.Path.GetFileName does not really do what the name says in certain circumstances. But we can use that behavior none the less.
Prerequisites
I have setup a consoleapplication with 2 folders and a file in each folder.
Something like this.
I set the file properties of Class1.vb and Class2.vb to Build Action -> None and Copy to Output Directory -> Copy Always.
Files
This is what you would use GetFileName for in most circumstances because that is the logical thing to do.
vbnet
Dim directories = System.IO.Directory.GetDirectories(Environment.CurrentDirectory)
For Each directory In directories
Dim files = System.IO.Directory.GetFiles(directory)
For Each File In files
Console.WriteLine(System.IO.Path.GetFileName(File))
Next
Next
Console.ReadLine()
csharp
var directories = System.IO.Directory.GetDirectories(Environment.CurrentDirectory);
foreach(var directory In directories)
{
var files = System.IO.Directory.GetFiles(directory);
foreach(var File In files)
{
Console.WriteLine(System.IO.Path.GetFileName(File));
}
}
Console.ReadLine()
Thsi would give you the following result.
Class1.vb
Class2.vb
Directories
But then I added this line of code.
Console.WriteLine(System.IO.Path.GetFileName(directory))
Like so.
vbnet
Dim directories = System.IO.Directory.GetDirectories(Environment.CurrentDirectory)
For Each directory In directories
Dim files = System.IO.Directory.GetFiles(directory)
For Each File In files
Console.WriteLine(System.IO.Path.GetFileName(File))
Next
Console.WriteLine(System.IO.Path.GetFileName(directory))
Next
Console.ReadLine()
csharp
var directories = System.IO.Directory.GetDirectories(Environment.CurrentDirectory);
foreach(var directory In directories)
{
var files = System.IO.Directory.GetFiles(directory);
foreach(var File In files)
{
Console.WriteLine(System.IO.Path.GetFileName(File));
}
Console.WriteLine(System.IO.Path.GetFileName(directory));
}
Console.ReadLine()
This gives the following result.
Class1.vb
NewFolder1
Class2.vb
NewFolder2
If I go read the MSDN article on this.
It says:
Return Value
Type: System.String
The characters after the last directory character in path. If the last character of path is a directory or volume separator character, this method returns String.Empty. If path is Nothing, this method returns Nothing.
So what I think they are doing is to check for the last directory or volumeseparator and then take what ever comes after that as the filename. I wonder why they do not check if that is a real file? That would be a very simple check and would really return a filename. Now it just returns anything that looks like a filename. Perhaps they should change it to GetPossibleFileName because that’s what it does.
Conclusion
When writing an API choose your methodnames carefully so they tell the user what they can expect. GetFileName does not return what I expect. Thank you for listening.
Chris is awesome.
