Start Debugging

Tag: errors

41 posts · Page 4 of 5

2026-05-11 errors csharp dotnet

Fix: dotnet ef migrations add fails with 'Unable to create an object of type DbContext'

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.

2026-05-11 errors csharp dotnet

Fix: MSB3027 Could not copy X to Y. Exceeded retry count of 10. Failed

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.

2026-05-11 errors csharp dotnet

Fix: The type or namespace name 'X' could not be found (after adding a project reference)

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.

2026-05-10 errors csharp dotnet

Fix: Cannot consume scoped service 'X' from singleton 'Y'

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.

2026-05-10 errors csharp dotnet

Fix: PlatformNotSupportedException: Operation is not supported on this platform in Native AOT

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.

2026-05-10 errors csharp dotnet

Fix: Unable to resolve service for type 'X' while attempting to activate 'Y'

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.

2026-05-09 errors csharp dotnet

Fix: TaskCanceledException: A task was canceled in HttpClient

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.

2026-05-08 errors csharp dotnet

Fix: The JSON value could not be converted to System.DateTime

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.

2026-05-07 errors csharp dotnet

Fix: The instance of entity type cannot be tracked because another instance with the same key value is already being tracked

EF Core 11 throws when two objects share a primary key inside one DbContext. Detach the old one or update it in place. AsNoTracking on the read prevents the collision.

2026-05-07 errors csharp dotnet

Fix: A second operation was started on this context instance before a previous operation completed

EF Core throws when two awaits run in parallel on the same DbContext. Await each call sequentially, or get a new DbContext per concurrent unit of work via IDbContextFactory.