csharp

Replace the Stream.Read or Write call with ReadAsync/WriteAsync. As a last resort, set AllowSynchronousIO on Kestrel, IIS, or per-request via IHttpBodyControlFeature.

Blazor's Razor compiler emits RZ10012 when a PascalCase tag has no matching component type in scope. Add @using for the component's namespace in _Imports.razor, or @namespace in the component, then rebuild.

EF Core's design-time tools could not instantiate your DbContext. Either expose a host via WebApplication.CreateBuilder, point to the right startup project, or implement IDesignTimeDbContextFactory.

MSB3027 means MSBuild retried a file copy 10 times and a process still held the destination. Kill the locking process, exclude bin/obj from antivirus, or raise CopyRetryCount.

CS0246 right after a fresh ProjectReference is almost always a TargetFramework mismatch, a stale obj folder, or a missing using directive. Five fixes in order of likelihood.

ASP.NET Core's scope validation throws this when a singleton would capture a scoped dependency for the rest of the process. Make the consumer scoped, or take IServiceScopeFactory and create a scope on demand.

Native AOT strips the JIT and the interpreter, so reflection emit, expression-tree compilation, and unseen MakeGenericType throw at runtime. Find the call via IL3050 and replace it with a source generator or a pre-baked path.

ASP.NET Core throws this when a constructor asks for a type that was never registered, was registered on the wrong container, or was added after the host was built. Three concrete fixes cover almost every case.

HttpClient throws TaskCanceledException for three different reasons: timeout, caller cancellation, or a connection-level abort. Tell them apart with InnerException and CancellationToken.IsCancellationRequested, then fix the right one.

System.Text.Json only accepts ISO 8601 strings for DateTime. Send 2026-05-08T14:00:00Z or register a JsonConverter that parses your format. Empty strings and Unix timestamps both throw.