Manipulate File Paths

Problem : You need to combine a filename with a directory name, or extract certain parts of a path.

Solution: You should almost never need to manually parse a path in C#. Instead, use the System.IO.Path class to perform your manipulation. This class has only static methods.

Table 1 details most of the methods and properties available to you.

Table 1. Path Methods and Properties

Method	Input	Output
GetDirectoryName()	C:\Windows\System32\xcopy.exe	C:\Windows\System32
GetExtension()	C:\Windows\System32\xcopy.exe	.exe
GetFileName()	C:\Windows\System32\xcopy.exe	xcopy.exe
GetFileNameWithoutExtension()	C:\Windows\System32\xcopy.exe	xcopy
GetFullPath()	xcopy.exe	C:\Windows\System32\xcopy.exe
Root()	C:\Windows\System32\xcopy.exe	C:\
HasExtension()	C:\Windows\System32\xcopy.exe	True
IsPathRooted()	C:\Windows\System32\xcopy.exe	True
IsPathRooted()	xcopy.exe	False
RandomFileName()	N/A	rq33lkoe.vwi
GetInvalidFileNameChars()	N/A	A long list of characters that are not allowed in filenames
GetInvalidPathChars()	N/A	A long list of characters that are not allowed in paths
AltDirectorySeparatorChar	N/A	‘/’
DirectorySeparatorChar	N/A	‘\’
PathSeparator	N/A	‘;’
VolumeSeparatorChar	N/A	‘:’

There are two additional useful methods. Path.Combine() will take two or more strings and combine them into a single path, inserting the correct directory separator characters where necessary. Here’s an example:

string path = Path.Combine(@"C:\Windows\", "System32", "xcopy.exe ");

This results in the path having the value "C:\Windows\System32\xcopy.exe ".

The second method, Path.ChangeExtension(), does just what you think it would. Here’s an example:

string path = Path.ChangeExtension(@"C:\Windows\System32\xcopy.exe ", "bin");

					    

The new value of path is "C:\Windows\System32\xcopy.bin". Note that this does not change the file on the disk—it’s just in the string.