How to use SHCreateItemFromParsingName with names from the shell namespace?

I am using SHCreateItemFromParsingName to turn a path into a IShellItem:

IShellItem ParseName(String path)
{
    IShellItem shellItem;

    HRESULT hr = SHCreateItemFromParsingName(path, null, IShellItem, out shellItem);
    if (Failed(hr)) 
        throw new ECOMException(hr);
    return shellItem;
}

Note: A IShellItem was introduced around 2006 to provide a handy wrapper around the Windows 95-era IShellFolder+pidl constructs. You can even ask a IShellItem to cough up it's underlying IShellFolder and pidl with the IParentAndItem.GetParentAndItem interface and method.

Different things have different display names

I can get ahold of some well-known locations in the shell namespace, and see their absolute parsing (SIGDN_DESKTOPABSOLUTEPARSING) and editing (SIGDN_DESKTOPABSOLUTEEDITING) display names:

Path	Editing	Parsing
C:\	"C:"	"C:"
C:\Windows	"C:\Windows"	"C:\Windows"
Desktop	"Desktop"	"C:\Users\Ian\Desktop"
Computer	"This PC"	"::{20D04FE0-3AEA-1069-A2D8-08002B30309D}"
Recycle Bin	"Recycle Bin"	"::{645FF040-5081-101B-9F08-00AA002F954E}"
Documents Library	"Libraries\Documents"	"::{031E4825-7B94-4DC3-B131-E946B44C8DD5}\Documents.library-ms" "
Startup	"C:\Users\Ian\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup"	"C:\Users\Ian\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup"

How to parse them when the user types in them in?

I can use IFileOpenDialog to let the user select one of these folders. But i'd really like the user to be able to type

"C:\Users"
"C:\Windows\Fonts"
"This PC"
"Recycle Bin"
"Libraries"
"Startup"
"Fonts"

and be able to parse it into an IShellItem.

The problem is that some of the paths are not parsed by SHCreateItemFromParsingName:

SHCreateItemFromParsingName("C:\"): Parses
SHCreateItemFromParsingName("C:\Windows"): Parses
SHCreateItemFromParsingName(""): Parses (but becomes "This PC")
SHCreateItemFromParsingName("This PC"): Fails
SHCreateItemFromParsingName("Recycle Bin"): Fails
SHCreateItemFromParsingName("Libraries"): Fails
SHCreateItemFromParsingName("OneDrive"): Fails
SHCreateItemFromParsingName("Libraries\Documents"): Fails
SHCreateItemFromParsingName("Network"): Fails
SHCreateItemFromParsingName("Startup"): Fails

Meanwhile, the IFileOpenDialog control that my program uses can parse them fine:

How can i parse the various special shell name places that a user might type in (that Windows Explorer and the IFileOpen dialog can parse) into an IShellItem for that folder?

The real question is that i want the user to be able to have a recent MRU list that contains things like:

C:\Windows
Recycle Bin
This PC

and be able to parse them later.

Solution

It would be interesting to debug Explorer and see how it does it.

My suggestion is; if the initial parse fails, prepend shell: to the path string and try parsing it again with SHParseDisplayName. If you set STR_PARSE_SHELL_PROTOCOL_TO_FILE_OBJECTS in the bind context you can also bind to special files. The shell: protocol is able to parse the internal/canonical name of special/known folders but I don't know if it also checks the display name.

Edit:

I had a chance to play around a bit now and the shell: prefix is not a huge improvement because it only checks the known folder canonical names:

PCWSTR paths[] = {
    TEXT("C:\\"),
    TEXT("C:\\Windows"),
    TEXT(""),
    TEXT("This PC"),
    TEXT("MyComputerFolder"), // Canonical KF name
    TEXT("Recycle Bin"),
    TEXT("RecycleBinFolder"), // Canonical KF name
    TEXT("Libraries"),
    TEXT("OneDrive"),
    TEXT("Libraries\\Documents"),
    TEXT("Network"),
    TEXT("NetworkPlacesFolder"), // Canonical KF name
    TEXT("Startup"),
};

OleInitialize(0);
INT pad = 0, fill, i;
for (i = 0; i < ARRAYSIZE(paths); ++i) pad = max(pad, lstrlen(paths[i]));
for (i = 1, fill = printf("%-*s | Original | shell:   |\n", pad, ""); i < fill; ++i) printf("-"); printf("\n");
for (i = 0; i < ARRAYSIZE(paths); ++i)
{
    WCHAR buf[MAX_PATH], *p1 = NULL, *p2 = NULL;
    IShellItem*pSI;
    HRESULT hr = SHCreateItemFromParsingName(paths[i], NULL, IID_IShellItem, (void**) &pSI);
    if (SUCCEEDED(hr)) pSI->GetDisplayName(SIGDN_DESKTOPABSOLUTEPARSING, &p1), pSI->Release();
    wsprintf(buf, L"shell:%s", paths[i]);
    HRESULT hr2 = SHCreateItemFromParsingName(buf, NULL, IID_IShellItem, (void**) &pSI);
    if (SUCCEEDED(hr2)) pSI->GetDisplayName(SIGDN_DESKTOPABSOLUTEPARSING, &p2), pSI->Release();
    wprintf(L"%-*s | %.8x | %.8x | %s\n", pad, paths[i], hr, hr2, p2 && *p2 ? p2 : p1 ? p1 : L"");
    CoTaskMemFree(p1), CoTaskMemFree(p2);
}

gives me this output:

                    | Original | shell:   |
-------------------------------------------
C:\                 | 00000000 | 80070003 | C:\
C:\Windows          | 00000000 | 80070003 | C:\Windows
                    | 00000000 | 80070003 | ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}
This PC             | 80070002 | 80070003 | 
MyComputerFolder    | 80070002 | 00000000 | ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}
Recycle Bin         | 80070002 | 80070003 | 
RecycleBinFolder    | 80070002 | 00000000 | ::{645FF040-5081-101B-9F08-00AA002F954E}
Libraries           | 80070002 | 00000000 | ::{031E4825-7B94-4DC3-B131-E946B44C8DD5}
OneDrive            | 80070002 | 80070003 | 
Libraries\Documents | 80070002 | 80070002 | 
Network             | 80070002 | 80070003 | 
NetworkPlacesFolder | 80070002 | 00000000 | ::{F02C1A0D-BE21-4350-88B0-7367FC96EF3C}
Startup             | 80070002 | 00000000 | C:\Users\Anders\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup

On Windows 8 SHCreateItemFromParsingName calls SHParseDisplayName (with STR_PARSE_AND_CREATE_ITEM and STR_PARSE_TRANSLATE_ALIASES) so even Microsoft have trouble separating parsing and display names in their API.

If you want to stay away from undocumented interfaces then you would have to add a third pass where you check the known folder display names. Or alternatively as Raymond Chen suggests in the comments; parse every path component manually against item display names in that IShellFolder.