How can I get the current user directory?

Try:

System.Environment.GetEnvironmentVariable("USERPROFILE");

Edit:

If the version of .NET you are using is 4 or above, you can use the Environment.SpecialFolder enumeration:

Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);

May be this will be a good solution: taking in account whether this is Vista/Win7 or XP and without using environment variables:

string path = Directory.GetParent(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData)).FullName;
if ( Environment.OSVersion.Version.Major >= 6 ) {
    path = Directory.GetParent(path).ToString();
}

Though using the environment variable is much more clear.

You can get the UserProfile path with just this:

Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);

Also very helpful, while investigating the Environment.SpecialFolder enum. Use LINQPad or create a solution and execute this code:

Enum.GetValues(typeof(Environment.SpecialFolder))
    .Cast<Environment.SpecialFolder>()
    .Select(specialFolder => new
    {
        Name = specialFolder.ToString(),
        Path = Environment.GetFolderPath(specialFolder)
    })
    .OrderBy(item => item.Path.ToLower())

This is the result on my machine:

MyComputer
LocalizedResources
CommonOemLinks
ProgramFiles            C:\Program Files (x86) 
ProgramFilesX86         C:\Program Files (x86) 
CommonProgramFiles      C:\Program Files (x86)\Common Files 
CommonProgramFilesX86   C:\Program Files (x86)\Common Files 
CommonApplicationData   C:\ProgramData 
CommonStartMenu         C:\ProgramData\Microsoft\Windows\Start Menu 
CommonPrograms          C:\ProgramData\Microsoft\Windows\Start Menu\Programs 
CommonAdminTools        C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Administrative Tools 
CommonStartup           C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup 
CommonTemplates         C:\ProgramData\Microsoft\Windows\Templates 
UserProfile             C:\Users\fisch 
LocalApplicationData    C:\Users\fisch\AppData\Local 
CDBurning               C:\Users\fisch\AppData\Local\Microsoft\Windows\Burn\Burn 
History                 C:\Users\fisch\AppData\Local\Microsoft\Windows\History 
InternetCache           C:\Users\fisch\AppData\Local\Microsoft\Windows\INetCache 
Cookies                 C:\Users\fisch\AppData\Local\Microsoft\Windows\INetCookies 
ApplicationData         C:\Users\fisch\AppData\Roaming 
NetworkShortcuts        C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Network Shortcuts 
PrinterShortcuts        C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Printer Shortcuts 
Recent                  C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Recent 
SendTo                  C:\Users\fisch\AppData\Roaming\Microsoft\Windows\SendTo 
StartMenu               C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Start Menu 
Programs                C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Start Menu\Programs 
AdminTools              C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Administrative Tools 
Startup                 C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup 
Templates               C:\Users\fisch\AppData\Roaming\Microsoft\Windows\Templates 
Desktop                 C:\Users\fisch\Desktop 
DesktopDirectory        C:\Users\fisch\Desktop 
Favorites               C:\Users\fisch\Favorites 
MyMusic                 C:\Users\fisch\Music 
MyDocuments             C:\Users\fisch\OneDrive\Documents 
MyDocuments             C:\Users\fisch\OneDrive\Documents 
MyPictures              C:\Users\fisch\OneDrive\Pictures 
MyVideos                C:\Users\fisch\Videos 
CommonDesktopDirectory  C:\Users\Public\Desktop 
CommonDocuments         C:\Users\Public\Documents 
CommonMusic             C:\Users\Public\Music 
CommonPictures          C:\Users\Public\Pictures 
CommonVideos            C:\Users\Public\Videos 
Windows                 C:\Windows 
Fonts                   C:\Windows\Fonts 
Resources               C:\Windows\resources 
System                  C:\Windows\system32 
SystemX86               C:\Windows\SysWoW64 

("fisch" is the first 5 letters of my last name. This is the user name assigned when signing in with a Microsoft Account.)

Environment.GetEnvironmentVariable("userprofile")

Trying to navigate up from a named SpecialFolder is prone for problems. There are plenty of reasons that the folders won't be where you expect them - users can move them on their own, GPO can move them, folder redirection to UNC paths, etc.

Using the environment variable for the userprofile should reflect any of those possible issues.