Long path support fails with Unicode characters even with LongPathsEnabled=1 in .NET on Windows

[Howard302]

Description

Even after enabling LongPathsEnabled in the Windows registry (set to 1 and system rebooted), .NET applications still fail to handle file paths that exceed the 260-character MAX_PATH limit and contain Unicode characters (Thai, Japanese, Russian, Greek, etc.).
Actual Behavior

• File operations throw PathTooLongException or DirectoryNotFoundException
• Drag-and-drop of such paths throws HRESULT: 0x8007007A (The data area passed to a system call is too small)
• Explorer.exe automatically redirects to default folders when path is too long
• .NET file APIs do not properly handle the \\?\ prefix for long path bypass
  Environment
• Windows 10/11 (latest version)
• .NET 6/7/8 (all versions affected)
• Reproduced in PCL 2(plain craft launcher)(a minecraft launcher) (C# .NET application) consistently

Reproduction Steps

1. Enable long path support in Windows:
   • Open regedit as administrator
   • Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem
   • Set LongPathsEnabled DWORD value to 1
   • Reboot the system
2. Create a test path longer than 260 characters with mixed Unicode characters:
   C:\test\ภาษาไทยカタカナРусскийΑλφαβητα\1\2\3\4\5\6\7\8\9\0\1\2\3\4\5\6\7\8\9\0\test.txt
3. Use .NET File.ReadAllText() or Directory.GetFiles() to access the path
4. Observe the exception/error
   Expected Behavior
   .NET should fully support long paths with Unicode characters when LongPathsEnabled is enabled, consistent with native Windows system behavior. The same path works correctly in PowerShell and native Win32 applications, confirming it's a .NET-specific bug.

Expected behavior

.NET should fully support long paths with Unicode characters when LongPathsEnabled is enabled, consistent with native Windows system behavior.
The same path works correctly in PowerShell and native Win32 applications, confirming it's a .NET-specific bug.

Actual behavior

• File operations throw PathTooLongException or DirectoryNotFoundException when accessing paths longer than 260 characters with Unicode characters
• Drag-and-drop of such paths throws HRESULT: 0x8007007A (The data area passed to a system call is too small)
• Explorer.exe automatically redirects to default folders when path is too long, even with LongPathsEnabled enabled
• .NET file APIs do not properly handle the \\?\ prefix for long path bypass

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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