Add DirectoryPath property to DirectoryNotFoundException

[ViveliDuCh]

Closes #103468

Adds a DirectoryPath property to DirectoryNotFoundException as approved in API review.

What's included

• DirectoryPath nullable property on DirectoryNotFoundException, matching the pattern of FileNotFoundException.FileName
• Two new constructors accepting directoryPath (message + directoryPath, message + directoryPath + innerException)
• Auto-constructed message when message is null but directoryPath is provided, via null-coalescing in the constructors
• ToString() override that includes DirectoryPath on a separate line
• Serialization support via GetObjectData / version-tolerant deserialization constructor
• Ref assembly updates for System.Runtime
• Updated Arg_DirectoryNotFoundException default message from "Attempted to access a path that is not on the disk." to "Unable to find the specified directory." to match FileNotFoundException's "Unable to find the specified file." pattern and align better with the new IO_DirectoryNotFound_Path string.
• Tests for all new constructors, property, message auto-construction, ToString() output, null edge cases, and serialization round-trip

Implementation notes

• Follows the FileNotFoundException implementation pattern:
  • The property is string? (nullable) because not all throw sites have a path available
  • The new constructors null-coalesce message (consistent with existing DNFE constructors), auto-constructing a descriptive message from directoryPath when message is null
• Uses managed SR.Format(...) for message construction rather than native interop, as recommended during API review
• Version-tolerant deserialization: iterates SerializationInfo entries to handle old payloads that lack the DirectoryPath field
• #if NET11_0_OR_GREATER guards on throw sites in multi-TFM files (Win32Marshal.cs, Interop.IOErrors.cs, PhysicalFileProvider.cs, LdapSessionOptions.Linux.cs) since the new constructor isn't available on older TFM targets

Internal throw-site updates

Updated 18 internal throw sites across 12 files to pass directory paths to the new constructors, so that DirectoryPath is populated for runtime-generated exceptions:

Area	File(s)	Path variable
CoreLib / Common	Win32Marshal.cs	path
CoreLib / Common	Interop.IOErrors.cs (Unix ENOTDIR)	path
CoreLib	FileInfo.cs (MoveTo)	directory of FullName
CoreLib	FileSystem.Unix.cs (×2, directory rename)	sourceFullPath
System.Formats.Tar	TarFile.cs (×8)	sourceDirectoryName / destinationDirectoryName
System.IO.IsolatedStorage	IsolatedStorageFile.cs	sourceDirectoryName
System.IO.FileSystem.AccessControl	FileSystemSecurity.cs	name
System.Net.Sockets	SocketAsyncEventArgs.Unix.cs	dirname
System.Security.AccessControl	NativeObjectSecurity.cs	name
System.DirectoryServices.Protocols	LdapSessionOptions.Linux.cs	value
Microsoft.Extensions.FileProviders.Physical	PhysicalFileProvider.cs	Root

Not updated (by design):

• 3 sites with no path available (SharedMemoryManager.Unix.cs default ctor, Interop.IOErrors.cs empty-path branch, FileSystemSecurity.cs null-name branch)
• 4 threading sites (EventWaitHandle, Mutex, EventWaitHandleAcl, MutexAcl) where the name is a named sync object, not a filesystem directory

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[Copilot]

Pull request overview

Adds a DirectoryPath property and related API surface to System.IO.DirectoryNotFoundException to enable machine-readable access to the missing directory path (similar to FileNotFoundException.FileName).

Changes:

• Added DirectoryPath property and new constructor overloads accepting directoryPath.
• Implemented Message and ToString() overrides to incorporate DirectoryPath (including auto-message when message is null).
• Added serialization support and updated reference assembly and tests.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/libraries/System.Private.CoreLib/src/System/IO/DirectoryNotFoundException.cs	Implements DirectoryPath property, new constructors, Message/ToString() overrides, and serialization plumbing.
src/libraries/System.Private.CoreLib/src/Resources/Strings.resx	Adds new localized strings used for message/to-string formatting.
src/libraries/System.Runtime/ref/System.Runtime.cs	Updates ref assembly to include the new constructors, property, and overrides.
src/libraries/System.Runtime/tests/System.Runtime.Tests/System/IO/DirectoryNotFoundExceptionTests.cs	Adds unit tests covering the new API surface and formatting behaviors.

[jkotas]

Optional follow-up

When we introduce new APIs that can be used within the BCL, we typically add their use within the BCL as part of same PR to validate that the API actually works well in practice.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.

[jozkee]

Otherwise; LGTM, thanks.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

[ViveliDuCh]

/ba-g Build Analysis stuck idle (2+ days, no re-run option). Failure is MacCatalyst infra issue: XHarness exit 82 (RETURN_CODE_NOT_SET), test runner couldn't read app exit code (empty log). Previous run passed.