Path

In VB.NET the Path type offers many useful Functions. They provide ways to manipulate strings that represent file paths. With Path, our main program logic can be kept simpler.

By using the Path type, we avoid writing a lot of string manipulation code over and over again. We can safely combine paths, and get parts of paths. This makes programs simpler.

Example

First we look at the result of the function Path.GetExtension. We also see GetFileName, GetFileNameWithoutExtension and GetPathRoot. The Imports line references the System.IO namespace.

Imports System.IO

Module Module1

    Sub Main()
        ' Input string.
        Dim value As String = "C:\stage.txt"

        ' Use Path methods.
        Dim extension As String = Path.GetExtension(value)
        Dim filename As String = Path.GetFileName(value)
        Dim filenameNotExtension As String = Path.GetFileNameWithoutExtension(value)
        Dim root As String = Path.GetPathRoot(value)

        ' Print results.
        Console.WriteLine(extension)
        Console.WriteLine(filename)
        Console.WriteLine(filenameNotExtension)
        Console.WriteLine(root)
    End Sub

End Module
.txt
stage.txt
stage
C:\

Example output

Sometimes, you will pass a path string that does not have an extension, a directory, or a volume. The separator character may not be the default one as well.

Imports System.IO

Module Module1
    Sub Main()
        Dim pages() As String = { _
            "cat.aspx", _
            "invalid-page", _
            "Content/Rat.aspx", _
            "http://dotnetperls.com/Cat/Mouse.aspx",
            "C:\Windows\File.txt",
            "C:\Word-2007.docx" _
        }

        For Each page As String In pages
            ' Write path function results.
            Console.Write(Path.GetFileName(page))
            Console.Write(", ")
            Console.Write(Path.GetFileNameWithoutExtension(page))
            Console.Write(", ")
            Console.Write(Path.GetDirectoryName(page))
            Console.WriteLine()
        Next
    End Sub
End Module
cat.aspx, cat,
invalid-page, invalid-page,
Rat.aspx, Rat, Content
Mouse.aspx, Mouse, http:\dotnetperls.com\Cat
File.txt, File, C:\Windows
Word-2007.docx, Word-2007, C:\

Combine path strings

With Path we can combine a directory string with a file name, with or without a trailing slash. The Path.Combine function handles both cases.

Imports System.IO

Module Module1
    Sub Main()
        ' Combine directory with file name.
        Dim value1 As String = Path.Combine("Content", "file.txt")
        Console.WriteLine(value1)

        ' Combine directory and trailing backslash with file name.
        Dim value2 As String = Path.Combine("Content\", "file.txt")
        Console.WriteLine(value2)
    End Sub
End Module
Content\file.txt
Content\file.txt

Separator characters

Several char members that represent separators. For example, the DirectorySeparatorChar is equal to "\", while the AltDirectorySeparatorChar is equal to "/".

Imports System.IO

Module Module1
    Sub Main()
        ' Write these chars to the screen.
        Console.WriteLine(Path.AltDirectorySeparatorChar)
        Console.WriteLine(Path.DirectorySeparatorChar)
        Console.WriteLine(Path.PathSeparator)
        Console.WriteLine(Path.VolumeSeparatorChar)
    End Sub
End Module
/
\
;
:

Temporary file paths

In many programs, you may want to write to a temporary file location. This is a temporary location because it will not be needed later for any reason.

Imports System.IO

Module Module1
    Sub Main()
        ' Write temp file names and then temp paths.
        Console.WriteLine(Path.GetTempFileName())
        Console.WriteLine(Path.GetTempFileName())
        Console.WriteLine()
        Console.WriteLine(Path.GetTempPath())
        Console.WriteLine(Path.GetTempPath())
    End Sub
End Module
C:\Users\Sam\AppData\Local\Temp\tmpF664.tmp
C:\Users\Sam\AppData\Local\Temp\tmpF665.tmp

C:\Users\Sam\AppData\Local\Temp\
C:\Users\Sam\AppData\Local\Temp\

Random file names

How can you generate a random file name? You might want to write to a secret location or create a unique file. Please invoke the Path.GetRandomFileName function.

Imports System.IO

Module Module1
    Sub Main()
        ' Output two random file names.
        Console.WriteLine(Path.GetRandomFileName())
        Console.WriteLine(Path.GetRandomFileName())
    End Sub
End Module
d5mgpsqn.gce
mseds0ay.1am

Extensions

When you call the Path.GetExtension method, your extension will contain the leading period. In other words, ".txt" is the extension for a text file, not "txt".

Summary

The Path functions are useful and provide error-correction in your programs. By using these methods, your programs will become more robust and more compact.