What’s New in .NET 11 Preview 1 & 2: Runtime Async, Zstandard, Blazor TempData, and Vector Search

.NET 11 Preview 1 and 2 introduce several significant improvements. Runtime Async V2 moves async/await state machine logic into the runtime itself, reducing overhead and improving diagnostics without code changes. Native Zstandard (zstd) compression is now built into the BCL, offering 2–7x faster decompression than GZip/Brotli. Blazor gains TempData support for static SSR, enabling flash messages and Post-Redirect-Get patterns. EF Core adds native SQL Server vector search via LINQ with DiskANN indexes, enabling semantic similarity queries. Additional highlights include BFloat16 for ML workloads, C# collection expression arguments, native OpenTelemetry tracing in ASP.NET Core, smaller SDK container images (up to 17%), MAUI/Android improvements with CoreCLR as default, and CLI enhancements to dotnet run, test, and watch.