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127 posts · Page 12 of 13

2026-05-13 errors csharp dotnet

Fix: System.Security.Cryptography.CryptographicException: Keyset does not exist

The certificate's private key lives in a separate Windows key file the current process identity cannot read. Grant ACL on the key, load the PFX with MachineKeySet, or use EphemeralKeySet.

2026-05-13 errors csharp dotnet

Fix: System.Text.Json.JsonException: The JSON value could not be converted

System.Text.Json throws this when the incoming JSON token doesn't match the CLR target type. Match the JSON to the type, or register a JsonConverter or JsonSerializerOption that bridges them.

2026-05-13 errors dotnet dotnet-11

Fix: The command 'dotnet' could not be found on CI

Your CI runner cannot resolve dotnet because the SDK is not installed for that step, or it is installed but not on PATH. Use actions/setup-dotnet, pin a global.json, and export DOTNET_ROOT and ~/.dotnet/tools.

2026-05-12 errors csharp dotnet

Fix: System.IO.FileNotFoundException: Could not load file or assembly in a published app

Runs fine with dotnet run, throws after dotnet publish. The DLL is usually missing from the publish folder, not the runtime. Check deps.json, ProjectReference Private, and trimming.

2026-05-12 errors csharp dotnet

Fix: InvalidOperationException: Synchronous operations are disallowed

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

2026-05-12 errors csharp dotnet

Fix: RZ10012: Found markup element with unexpected name in Blazor

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.

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.