csharp

Zstandard is the right default for dynamic API responses in .NET 11, but not at the quality the ASP.NET Core provider ships with. Benchmarks on real JSON payloads showing why quality 1 beats the default quality 3 on both size and CPU, when Brotli still wins, and why Gzip survives only as a fallback.

Microsoft.Extensions.AI 10.9.0 adds RoutingChatClient, OrderedFailoverChatClient, and SemanticRoutingChatClient. Verified against the real package: what fails over, what does not, and why MEAI001 breaks your build.

Labeled break and continue landed in the C# section of .NET 11 Preview 7. You can now put a label on a loop and jump straight to it, which retires the bool flag and goto workarounds for nested loops.

Two different things get called a modal window in .NET MAUI 11. PushModalAsync gives you a modal page on every platform. A real OS window that disables its owner has no MAUI API at all, so here is the WinUI OverlappedPresenter.IsModal plus Win32 owner-handle interop that actually works on Windows, and what to do on Mac Catalyst instead.

Attach a JsonTypeInfo modifier to a source-generated JsonSerializerContext in .NET 11: why new MyContext(options) silently drops it, the WithAddedModifier setup that works, the fast path you give up (measured), and the naming-policy trap that makes modifiers no-op.

A complete guide to file-based C# apps: running a single .cs file with dotnet run, the #:package, #:sdk, #:property, #:project and #:include directives, multi-file scripts with #:ref, argument and stdin handling, the build cache, native AOT publishing, packaging as a dotnet tool, and dotnet project convert when the script outgrows itself.

Replace UseSwaggerUI with MapScalarApiReference in ASP.NET Core 11: routing, multiple documents, pre-filled auth, production gating, offline assets, and the Scalar-only OpenAPI extensions that mark endpoints stable or hidden.

Replace a hand-rolled classifier-plus-switch router with AgentWorkflowBuilder.CreateHandoffBuilderWith in Microsoft.Agents.AI.Workflows 1.17.0. What breaks, the six migration steps, and the gotchas around agent Ids, descriptions, and context broadcast.

For internal service-to-service calls in .NET 11, default to gRPC when you own both ends of the contract and the call is point-to-point. Use REST with JSON when anything you do not control has to call the service. SignalR is not an RPC transport between services: reach for it only when one producer has to fan a message out to many long-lived consumers.

Use declarative YAML when the graph is a sequential routing decision that non-developers change often. Use code-first WorkflowBuilder the moment you need parallelism, custom executors, or a non-Foundry agent. Here is the decision, the action catalog limits, and the code both ways.