CurrentCultureIgnoreCase string compare return false with Culture "en-US-POSIX"

[wli3]

Please close if this is by design of "en-US-POSIX". I want to make sure this is intentional. It is odd that a culture with prefix "en-US" will return false when comparing "nukeeper" and "NuKeeper"

public static void Main(string[] args)
{
    CultureInfo.CurrentCulture = new CultureInfo("en-US-POSIX");
    Console.WriteLine("CurrentCulture is {0}.", CultureInfo.CurrentCulture.Name);
    Console.WriteLine(string.Compare("nukeeper", "NuKeeper", StringComparison.CurrentCultureIgnoreCase) == 0);
}

[stephentoub]

cc: @tarekgh

(Tarek, is there a FAQ somewhere about POSIX/C culture handling that we can point people to? The question seems to come up a lot. If there's not already a discussion in the docs, maybe there could be?)

[tarekgh]

@wli3 please look at the comment on the issue https://github.com/dotnet/corefx/issues/32250#issuecomment-420749205

@stephentoub I'll log issue to get this in the official documentation instead.

[tarekgh]

logged the issue dotnet/docs#8179

[nguerrera]

In https://github.com/dotnet/cli/issues/10101, this seems to be happening by default on Unbuntu 18.04 on WSL.

Should we be following up with WSL folks to make sure this isn't the default there? The docs issue says "We need to discourage users from using C or Posix cultures and always replace such usage with some other culture like en-US". In this case, I don't think the user has done anything deliberate, they're just using .NET Core on WSL.

[tarekgh]

@nguerrera this is a good idea. if you have a contact from WSL we can contact them.

[nguerrera]

cc @bitcrazed

[nguerrera]

What is it about WSL that causes it to have this culture by default? An environment variable?