DirectoryNotFoundException reports wrong path

[janseris]

Description

string companyName = "My company d.o.o.";
string productName = "My product name";
string localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
string applicationLocalAppData = Path.Combine(localAppData, companyName, productName);
Console.WriteLine(localAppData);
Console.WriteLine(applicationLocalAppData);
string fileName = "1.png";
string filePath =  Path.Combine(applicationLocalAppData, fileName);
Console.WriteLine(filePath);
File.WriteAllBytes(filePath, [] /* empty */);

try { File.WriteAllBytes(filePath, [] /* empty */); } catch (Exception ex) { Console.WriteLine(ex.Message); }

Reproduction Steps

Run as .NET 8 console app with top-level statements

Expected behavior

path matches

Actual behavior

dot is missing in company name in reported exception

Regression?

No response

Known Workarounds

No response

Configuration

C:\Users\Jan>dotnet --version
9.0.203

Windows 11

Microsoft Visual Studio Community 2022
Version 17.13.6
VisualStudio.17.Release/17.13.6+35931.197
Microsoft .NET Framework
Version 4.8.09032

Installed Version: Community

C# Tools 4.13.0-3.25167.3+73eff2b5de2ad38ec602c0a9e82f9125fb85992b
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

</Project>

Other information

No response

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[elgonzo]

I think the exception is correct.

You provided a path with a directory ending with a dot. Directory/file names ending with a dot are not commonly supported on Windows (aside from the old "NTFS file name with secondary data stream name" trick, i don't know if there are exploitable Windows APIs for sneakily creating such directories/files).

When you pass such a path, trailing dots are removed from the path components and then the path without the trailing dot(s) is being used. You can observe this elsewhere outside of .NET, too -- for example using the CMD prompt, or the Windows explorer, or using native WINAPIs like CreateFile/CreateDirectory/CreateDirectoryEx/etc... directly.

In this sense, the exception is correct because it reports on the path that is actually being used for attempting to access the file system entry.

[janseris]

I think the exception is correct.

You provided a path with a directory ending with a dot. Directory/file names ending with a dot are not commonly supported on Windows (aside from the old "NTFS file name with secondary data stream name" trick, i don't know if there are exploitable Windows APIs for sneakily creating such directories/files).

When you pass such a path, trailing dots are removed from the path components and then the path without the trailing dot(s) is being used. You can observe this elsewhere outside of .NET, too -- for example using the CMD prompt, or the Windows explorer, or using native WINAPIs like CreateFile/CreateDirectory/CreateDirectoryEx/etc... directly.

In this sense, the exception is correct because it reports on the path that is actually being used for attempting to access the file system entry.

Thanks, I see. When you create a directory ending with dot, the trailing dot is removed from the name before creating the directory.