When developing Windows Applications it is quite common to end up having to access a special folder. Some examples of special folders are user Desktop, user Documents (My Documents in case of Windows XP), temporary folder, etc. When using the file system I/O functions it is important to always access the correct folder thus one cannot assume that for example the user Desktop is always located at “C:\Users\<user name>\Desktop” or “C:\Documents and Settings\<user name>\Desktop”.

Part 1: The most generic way of accessing special folders

Windows provides environmental variables to access special folders, for example %HOMEPATH% to access the user folders and %PROGRAMFILES% to access the Program Files folder. These environmental variables can be used in .NET to obtain the correct folder location for special folders.

The complete list of common environmental variables can be obtained from “Using Environemnt variables in cmd.exe” article on MSDN. For quick referencing we have taken the relevant excerpt from MSDN and appended it at the end of this article.

In order to use the environmental variables from .NET code one has to use the method

System.Environment.ExpandEnvironmentVariables(string)

The static method ExpandEnvironmentVariables() converts all environment variables within the specified path to their correct value.

Example 1:

For example, consider you need to access the user Desktop, the C♯ code to do so is

Example 2:

Consider you want to read a text file residing in the user local profile.

The drawback of this approach is that some environment variables might not exist on all platforms or the way the paths are returned change slightly from one platform to another.

Part 2: Using .NET enumerations

Another way of accessing special folders in .NET is to use

enumerations. These enumerations provide a reliable way of accessing special folders on different platforms. Values from this enumeration can be used with the method

Taking the same examples used in Part 1, the code using the GetFolderPath() method will look like

Example 1:

For example, consider you need to access the user Desktop, the C♯ code to do so is

Example 2:

Consider you want to read a text file residing in the user local profile.

When comparing the code in Path 1 and the code above it is clear that there is no structural change. However, using the GetFolderPath() method provides a more reliable and access to more special folders as it removes the operating system dependency from code.

Part 3: The exception

The temporary folder is the mostly used folder. .NET provides another alternative way of accessing the temporary folder. System.IO.Path.GetTempPath() method returns the system?s temporary folder. Using this method guarantee?s that when writing or reading files stored in the temporary folders you always access the current temporary folder.

References:

• MSDN: Using Environemnt variables in cmd.exe
• MSDN: System.IO.Path
• MSDN: System.Environment
• Clounce.com: Combining Directory Paths

Excerpt from MSDN: Using Environemnt variables in cmd.exe article