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Tag: aspnetcore

72 posts · Page 4 of 8

2026-07-09 migration aspnetcore dotnet-11

Migrate a minimal API from manual validation checks to built-in validation in ASP.NET Core 11

A step-by-step migration guide for replacing hand-rolled if-checks in ASP.NET Core 11 minimal API handlers with the built-in source-generated DataAnnotations validator: what breaks, which manual rules do and do not port, and how to verify the 400 ProblemDetails contract stays identical.

2026-07-06 errors dotnet dotnet-11

Fix: "415 Unsupported Media Type" from a minimal API endpoint in ASP.NET Core 11

A minimal API returns 415 when the request Content-Type does not match what the endpoint binds. Send Content-Type: application/json for a body-bound type, or use [FromForm] for form and file uploads.

2026-07-03 csharp dotnet dotnet-11

How to customize minimal API validation error responses with IProblemDetailsService in ASP.NET Core 11

Call AddProblemDetails with a CustomizeProblemDetails callback to reshape the 400 that built-in minimal API validation returns in ASP.NET Core 11: add a traceId, rewrite the title, switch 400 to 422, or take full control with a custom IProblemDetailsWriter.

2026-07-03 csharp dotnet dotnet-11

How to set up JWT bearer authentication in a minimal API in ASP.NET Core 11

A complete, working setup for JWT bearer authentication in an ASP.NET Core 11 minimal API: install the package, wire up AddAuthentication().AddJwtBearer(), issue a token, protect endpoints with RequireAuthorization, add role and claim policies, and test the whole thing with dotnet user-jwts.

2026-06-26 comparison aspnetcore dotnet

JWT vs cookie authentication in ASP.NET Core 11: which should you pick?

Use cookie authentication for any app where the browser is the only client, and reserve JWT bearer tokens for APIs called by mobile apps, other services, or third parties. Here is the full decision matrix.

2026-06-25 csharp dotnet dotnet-11

Why your ASP.NET Core JWT returns 401 even with a valid token

A valid token that still 401s almost always means the bearer handler never ran or ran under the wrong scheme. Check middleware order, the default scheme, the scheme name, and whether the header even reached the handler.

2026-06-25 errors csharp dotnet

Fix: 405 Method Not Allowed instead of 401 with JWT bearer in ASP.NET Core

A protected endpoint returning 405 instead of 401 almost always means routing rejected the HTTP verb before auth ran, or a cookie scheme stole the challenge. Here is how to tell which.

2026-06-23 csharp dotnet dotnet-11

How to register and resolve keyed services in .NET 11 dependency injection

Register more than one implementation of the same interface under a key with AddKeyedSingleton/Scoped/Transient, then resolve them with [FromKeyedServices], GetRequiredKeyedService, or KeyedService.AnyKey. The keyed and non-keyed registries are separate, which is the gotcha that bites most people.

2026-06-22 csharp dotnet dotnet-11

How to validate a JWT's issuer, audience, and lifetime in ASP.NET Core 11

A complete guide to TokenValidationParameters in ASP.NET Core 11: how ValidateIssuer, ValidateAudience, and ValidateLifetime work, what the defaults actually are, why Authority auto-configures the issuer and signing keys, the 5-minute ClockSkew trap, and how to read the IDX error codes when a valid-looking token is rejected.

2026-06-21 csharp dotnet dotnet-11

How to configure CORS for a JWT-protected API in ASP.NET Core 11

A complete guide to CORS for a bearer-token API in ASP.NET Core 11: the correct UseCors ordering relative to authentication, why a bearer token in the Authorization header is not a CORS credential, why AllowAnyHeader works but a manual wildcard does not cover Authorization, and how to keep preflight from failing.