Environment.GetFolderPath() doesn't support all KNOWNFOLDERID's

[sba923]

(Redirecting from (PowerShell/PowerShell#11240))

It should be possible to retrieve the location of all "special folders" instead of hardcoding them (or assuming they are just subfolders of the user's profile folder).

As of today, Environment.GetFolderPath() (which reportedly relies on SHGetKnownFolderPath()) doesn't support all KNOWNFOLDERID's. Here's a few of the ones that are not supported:

FOLDERID_Downloads
FOLDERID_DocumentsLibrary
FOLDERID_CameraRoll

This piece of code

using System;

namespace GetFolderPath
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (Environment.SpecialFolder folder in (Environment.SpecialFolder[]) Enum.GetValues(typeof(Environment.SpecialFolder)))
            {
                Console.WriteLine("{0,-30}{1}", folder, Environment.GetFolderPath(folder));
            }
        }
    }
}

outputs only this subset of folder paths:

Desktop                       C:\Users\joe\Desktop
Programs                      C:\Users\joe\AppData\Roaming\Microsoft\Windows\Start Menu\Programs
MyDocuments                   C:\Users\joe\Documents
MyDocuments                   C:\Users\joe\Documents
Favorites                     C:\Users\joe\Favorites
Startup                       C:\Users\joe\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
Recent                        C:\Users\joe\AppData\Roaming\Microsoft\Windows\Recent
SendTo                        C:\Users\joe\AppData\Roaming\Microsoft\Windows\SendTo
StartMenu                     C:\Users\joe\AppData\Roaming\Microsoft\Windows\Start Menu
MyMusic                       C:\Users\joe\Music
MyVideos                      C:\Users\joe\Videos
DesktopDirectory              C:\Users\joe\Desktop
MyComputer                    
NetworkShortcuts              C:\Users\joe\AppData\Roaming\Microsoft\Windows\Network Shortcuts
Fonts                         C:\windows\Fonts
Templates                     C:\Users\joe\AppData\Roaming\Microsoft\Windows\Templates
CommonStartMenu               C:\ProgramData\Microsoft\Windows\Start Menu
CommonPrograms                C:\ProgramData\Microsoft\Windows\Start Menu\Programs
CommonStartup                 C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup
CommonDesktopDirectory        C:\Users\Public\Desktop
ApplicationData               C:\Users\joe\AppData\Roaming
PrinterShortcuts              
LocalApplicationData          C:\Users\joe\AppData\Local
InternetCache                 C:\Users\joe\AppData\Local\Microsoft\Windows\INetCache
Cookies                       C:\Users\joe\AppData\Local\Microsoft\Windows\INetCookies
History                       C:\Users\joe\AppData\Local\Microsoft\Windows\History
CommonApplicationData         C:\ProgramData
Windows                       C:\windows
System                        C:\windows\system32
ProgramFiles                  C:\Program Files
MyPictures                    C:\Users\joe\Pictures
UserProfile                   C:\Users\joe
SystemX86                     C:\windows\SysWOW64
ProgramFilesX86               C:\Program Files (x86)
CommonProgramFiles            C:\Program Files\Common Files
CommonProgramFilesX86         C:\Program Files (x86)\Common Files
CommonTemplates               C:\ProgramData\Microsoft\Windows\Templates
CommonDocuments               C:\Users\Public\Documents
CommonAdminTools              C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Administrative Tools
AdminTools                    C:\Users\joe\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Administrative Tools
CommonMusic                   C:\Users\Public\Music
CommonPictures                C:\Users\Public\Pictures
CommonVideos                  C:\Users\Public\Videos
Resources                     C:\windows\resources
LocalizedResources            
CommonOemLinks                
CDBurning                     C:\Users\joe\AppData\Local\Microsoft\Windows\Burn\Burn

[danmoseley]

Looks like this is because on .NET Framework, Environment.GetFolderPath() uses ShGetFolderPath which cannot give you the downloads folder (it has no CSIDL value). On .NET Core, perhaps to accommodate long paths, we already changed to ShGetKnownFolderPath. This takes KNOWNFOLDERID and Downloads has one of these.

This is essentially an API request for new members of Environment.SpecialFolders. Someone interested in this should make a list of proposed additions. Note that they ideally all have some meaning on Mac and Linux. We should not add "CameraRoll" unless it's actually important. Downloads seems pretty basic though.

[ChadSimmons]

If it's documented, I recommend including it since determining importance is a fool's errand. For example, CameraRoll might not be important to many, but since it is included in One Drive Known Folder Move it is of interest to people trying to use that.
Definitely include

• CameraRoll
• Screenshots

[danmoseley]

If it's documented, I recommend including it since determining importance is a fool's errand.

Maybe if Windows was the only relevant OS, but it is not: as the list gets longer there are more entries without clear mappings on various Linux distros, macOS, Android, iOS, etc. We can take guesses or return empty string but that potentially makes life harder for folks trying to target those OS, who must now figure out which members of the enumeration are going to be useful. Eg., what should CameraRoll return on Ubuntu? Maybe there is no mapping, or several possible mappings. If I'm writing a photo editor app, should I offer it in my "open file" picker?

We are already returning empty string in quite a few cases for Unix

runtime/src/libraries/System.Private.CoreLib/src/System/Environment.GetFolderPathCore.Unix.cs

Line 143 in 2d4acbd

return string.Empty;

And for example on about 30 cases on iOS
https://github.com/mono/mono/blob/c5b88ec4f323f2bdb7c7d0a595ece28dae66579c/mcs/class/corlib/System/Environment.iOS.cs#L91

[sba923]

Sure, Windows is not the only targeted OS. I'm a great advocate of non-Windows .NET Core / PowerShell.

But OTOH, not all code / scripts is / are written to be xplat!

I hate that I have to write weird code (mainly on Windows) to determine where the Downloads folder resides...

[danmoseley]

It would be good to improve the doc so it has a big table showing what works on what platform. It looks like it's not been updated for cross plat.

https://docs.microsoft.com/en-us/dotnet/api/system.environment.specialfolder?view=netcore-3.1

[sba923]

Yes! And that big table would have Windows-only entries ;-) Or "not MacOS" entries. Whatever.