Creating symbolic links without developer mode or elevation fails silently

[jozkee]

Tested on Windows 10 21H1 19043 without Developer Mode with .NET 6 RTM; it does not throw.

Originally posted by @wegylexy in #57205 (comment)

cc @iSazonov @adamsitnik.

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Issue Details

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Tested on Windows 10 21H1 19043 without Developer Mode with .NET 6 RTM; it does not throw.

Originally posted by @wegylexy in #57205 (comment)

Author:	Jozkee
Assignees:	-
Labels:	area-System.IO, untriaged
Milestone:	-

[jozkee]

The Windows API CreateSymbolicLinkW is silently failing and we just return what the API reports.

Posible options to deal with this:

• Contact Windows team and discuss if they can fix CreateSymbolicLinkW.

• After calling FileSystemInfo link = File.CreateSymbolicLink("link", "target");
  Check link.Exists in order to verify that it was indeed created. This also works as a workaround for its current state.

• Is very likely that CreateSymbolicLinkW uses DeviceIoControl, we can investigate if using that function for symlink creation is more reliable.
  As a side note: we already use on FileSystemInfo.LinkTarget.

[iSazonov]

If Windows team can not fix old (supported) Windows versions it is best to use DeviceIoControl and backport to .Net 6 as bug fix.

[wegylexy]

I have something on production that assumes it doesn't throw and checks for existence afterwards. A user reports it throws on Windows 7 when not run as admin.