csharp

On container protocol 2.0.0, Foundry hosted agents isolate conversations and sessions per Entra caller by default. When your own backend fronts many end users, you delegate with x-ms-user-identity, grant a custom impersonation role, and key everything your container stores by session ID plus user ID. Here is the C# for each layer and the traps that leak data between users.

Use the en-IN culture or set NumberFormatInfo.NumberGroupSizes to [3, 2] to print 12,34,56,789 instead of 123,456,789 in C#. Measured on .NET 10 and .NET 11 RC1: how the array works, why CurrencyGroupSizes is separate, the invariant-globalization trap that silently prints Western grouping, and a lakh/crore words helper.

Microsoft.Extensions.Telemetry 10.11.0, released October 15, 2026, adds an experimental IncludeScopes option to global and per-request log buffering, so OrderId and TenantId from BeginScope survive a Flush() instead of being silently dropped.

A with expression calls the record's compiler-generated <Clone>$ method, which runs a copy constructor that copies every instance field and skips all initializers. That is why properties initialized from other properties, cached values, and Guid IDs come out stale. Measured on .NET 10 with C# 14, with the fixes that actually work.

A source-breaking change stops consumer code from compiling the next time it is rebuilt; a binary-breaking change makes already-compiled consumers fail at run time with MissingMethodException, MissingFieldException or TypeLoadException. Measured on .NET 10 with a v1/v2 DLL swap, plus what package validation catches and what it misses.

Understand C# reference escape rules with compiler-checked examples for ref locals, reassignment, scoped references and heap-backed versus stack-backed spans.

System.Formats.Cbor 11.0.0-rc.2 adds isFinalBlock, NeedsMoreData, and SlideData to CborReader, so you can decode CBOR straight off a stream without buffering the whole document. Verified on SDK 11.0.100-rc.2.

On an SMB or NFS share, polling is the source of truth and FileSystemWatcher is at best a hint. FileSystemWatcher misses remote changes on Linux and macOS, overflows its 64 KB network buffer, and stops for good when the connection drops. Use a periodic snapshot diff, and let the watcher only trigger an early scan. Verified on .NET 10.0.10.

Use await Task.Delay for any timed wait in async code, Thread.Sleep only on a dedicated thread you own, and SpinWait only for sub-microsecond waits inside lock-free code. To wait for a condition, use a signal (ManualResetEventSlim, SemaphoreSlim, TaskCompletionSource) instead of any of the three. Measured on .NET 10.0.10.

FileInfo caches its size, enumeration reads NTFS's lazily updated directory entry, and the writer may still hold bytes in its own buffers. Refresh(), or better, read the length from a shared handle with RandomAccess.GetLength.