`Path.Combine`, `HasExtension`, `GetFileName` docs still describe .NET Framework volume-separator (`:`) handling

[ForNeVeR]

Type of issue

Outdated article

Description

Several docs related to System.IO.Path APIs describe special handling of the volume separator (:) that modern .NET removed in .NET Core 2.1.

Path.Combine: the remarks for Combine(string, string), Combine(string, string, string), Combine(string, string, string, string) and Combine(params string[]) say a separator is appended only if the preceding path "is not a drive reference (that is, "C:" or "D:")" and does not end in DirectorySeparatorChar, AltDirectorySeparatorChar, or VolumeSeparatorChar. On .NET Core 2.1+ only DirectorySeparatorChar/AltDirectorySeparatorChar are checked, and no drive references:

Call	.NET 10	.NET Framework 4.x
Path.Combine("C:", "foo")	C:\foo	C:foo
Path.Combine("C:", "foo", "bar")	C:\foo\bar	C:foo\bar
Path.Combine(new[] { "C:", "foo" })	C:\foo	C:foo

The fixed-arity overloads changed in dotnet/coreclr#15579, and the params string[] overload in dotnet/coreclr#16447. Discussion in dotnet/runtime#27535 confirms that the change was intentional.

The same PR, dotnet/coreclr#16447, has adjusted behavior of several other APIs in a similar manner (removed special treatment of :), invalidating some other remarks:

• HasExtension (both overloads): return value and remarks say the search stops at VolumeSeparatorChar. It no longer does: Path.HasExtension(@"C:\a.b:c") is true on .NET 10 and false on .NET Framework.
• GetFileName (both overloads): says the result is empty when the path ends in a volume separator. Only a drive root counts now: Path.GetFileName(@"C:\file.txt:stream") returns file.txt:stream on .NET 10 and stream on .NET Framework; Path.GetFileName("foo:") returns foo: on .NET 10 and an empty string on .NET Framework. (The string overload's remarks already list only DirectorySeparatorChar/AltDirectorySeparatorChar, which contradicts its own return-value text.)

Proposal: describe the modern behavior (only DirectorySeparatorChar/AltDirectorySeparatorChar are treated as separators; a drive reference such as C: is still recognized at the start of a path, but not treated specifically by the affected APIs, e.g. Path.Combine). Add notes on the volume-separator behavior being specific .NET Framework only.

Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.io.path.combine?view=net-10.0#system-io-path-combine(system-string-system-string)

Content source URL

https://github.com/dotnet/dotnet-api-docs-temp/blob/live/xml/System.IO/Path.xml

Document Version Independent Id

fe224bbb-0eec-28fe-93e4-80a25b795e62

Platform Id

3916d1a3-5b50-d6c3-65d1-d12ac54cc834

Article author

@dotnet-bot