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2026-11-06 dotnet csharp dotnet-11

Why does Math.Round(2.5) return 2 in C#?

Math.Round uses banker's rounding (MidpointRounding.ToEven) by default, so 2.5 rounds to 2 and 3.5 rounds to 4. How to get 'school' rounding with AwayFromZero, why Math.Round(2.675, 2) still gives 2.67, how .NET 11 changed Math.Round(double, digits) to round the exact binary value, and why ToString("F2") disagrees with decimal formatting. Verified on .NET 10.0.14 and .NET 11 RC3.

2026-11-06 dotnet csharp dotnet-10

Why does string.GetHashCode() return a different value every run in .NET?

Since .NET Core, string.GetHashCode() is seeded with a random per-process value (Marvin hashing), so the same string hashes differently in every process. Why the runtime does it, which types are affected (HashCode.Combine, ValueTuple, records with string members), how Dictionary<string, T> quietly avoids the cost, and how to get a stable hash with XxHash3 or FNV-1a, verified on .NET 10.0.10.

2026-11-05 github-actions ci security

GitHub Actions blocks pull_request_target by default on December 2: what public .NET repos must check

Starting December 2, 2026, GitHub Actions blocks pull_request_target events in all public repositories unless an Actions event policy allows them. Brownouts hit on November 9 and 16. Here is how to find affected workflows and either migrate to pull_request or opt back in.

2026-11-05 aspnetcore dotnet rate-limiting

Why is the first limiter in PartitionedRateLimiter.CreateChained called twice per request?

ChainedPartitionedRateLimiter walks each limiter once, but the ASP.NET Core rate limiting middleware calls the chain twice when the first pass fails: AttemptAcquire, then AcquireAsync. With fixed window or token bucket limiters a rejected request burns two permits from the first limiter, and a queued request does too. Reproduced on ASP.NET Core 10.0.10 and 11.0 RC3, with a wrapper that makes the middleware walk the chain once.

2026-11-04 nuget dotnet agent-skills

NuGet Packages Can Now Carry Agent Skills: What Lives in the skills/ Folder

On November 3, 2026 the .NET team showed agent skills shipping inside NuGet packages as skills/<name>/SKILL.md. Here is the layout, how restore exposes it through project.assets.json, the two tools that read it today, and what is still missing.

2026-11-04 csharp dotnet garbage-collection

What happens if you start a thread from a finalizer in .NET?

Starting a thread inside a finalizer works, but the new thread is a normal-priority foreground thread that resurrects the object, outlives GC.WaitForPendingFinalizers, can crash the process, and may touch objects that were already finalized. Blocking on it hangs shutdown. Eight cases reproduced on .NET 10 with real output, plus the safe handoff pattern.

2026-11-04 csharp dotnet async

What is AsyncLocal<T>, and why doesn't a value set inside an awaited method flow back to the caller?

AsyncLocal<T> stores a value in the ExecutionContext, which flows down into awaits, Task.Run and continuations but never back up: every async method restores the caller's context when it returns. Verified on .NET 10: eleven cases with real output, the runtime code that does the restore, and three patterns that do get a value back to the caller.

2026-11-04 csharp dotnet performance

When is Stopwatch not high resolution in .NET, and what do IsHighResolution and Frequency report on each OS?

On .NET Core and .NET 5+ Stopwatch.IsHighResolution is a hard-coded true and never false. Frequency is whatever QueryPerformanceFrequency says on Windows (usually 10 MHz) and a fixed 1,000,000,000 on Linux, macOS, iOS, Android and WASM, which is a unit, not a resolution. Only .NET Framework can fall back to DateTime. Source walkthrough plus a measured run on .NET 10 / Apple M4 showing 1 ns nominal ticks but 41.67 ns real steps.

2026-11-03 blazor aspnetcore dotnet

Syncfusion Blazor Toolkit 2.0.1: 17 MIT Components, No License Key, No Data Grid

On October 29, 2026 Microsoft announced Syncfusion as a Blazor contributor. The headline is Syncfusion.Blazor.Toolkit 2.0.1: 17 MIT-licensed components for net8.0, net9.0 and net10.0, free for commercial use with no license key. Here is what is in it, how to wire it up, and where the commercial line is drawn.

2026-11-03 csharp dotnet attributes

What does [CallerArgumentExpression] capture, and how do I use it in my own guard methods?

[CallerArgumentExpression] makes the C# compiler pass the source text of an argument as a string. Verified on .NET 10 and C# 14: what exactly gets captured (whitespace, comments, parentheses, line breaks), when you get null instead, how to write NotNull, Positive and That guards, and the overload trap that silently disables it.