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Tag: dotnet-11

168 posts · Page 2 of 17

2026-06-25 errors csharp dotnet

Fix: The seed entity for entity type 'X' cannot be added because a non-zero value is required for property 'Id'

HasData seeds an entity with a store-generated key but no explicit value. Give every seed row a stable non-zero Id, or switch to UseSeeding for generated keys.

2026-06-24 how-to csharp csharp-14

How to declare extension properties in C# 14

Extension properties land in C# 14 through the new extension block. Declare get-only, settable, static, and generic extension properties, why auto-properties are rejected, and how the compiler lowers them to get_/set_ accessors.

2026-06-23 dotnet dotnet-11

.NET 11 Preview 5 lets file-based apps reference each other with `#:ref`

.NET 11 Preview 5 adds the #:ref directive so a dotnet run script can reference another file-based app as a library, with transitive references and no project file.

2026-06-23 how-to ef-core ef-core-11

How to do keyset (cursor) pagination in EF Core 11

Replace Skip/Take with a WHERE clause that seeks past the last row you saw. Order by a fully unique key, carry the last row's values as a cursor, and EF Core 11 turns the next page into an index seek instead of an OFFSET scan.

2026-06-23 how-to ef-core ef-core-11

How to map and query JSON columns in EF Core 11

Map a nested type to a single JSON column with ComplexProperty(...).ToJson(), let EF Core 11 store it in the native SQL Server 2025 json type, then query into it with LINQ that translates to JSON_VALUE, JSON_CONTAINS, and JSON_PATH_EXISTS.

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 csharp-15

C# 15 Closed Class Hierarchies: The closed Keyword in .NET 11 Preview 5

C# 15 adds the closed modifier in .NET 11 Preview 5, giving class hierarchies compile-time exhaustiveness in switch expressions. Here is how it works and the one gotcha.

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.

2026-06-20 csharp dotnet async

What is ValueTask<T> and when is it worth it?

ValueTask and ValueTask<T> are structs that let an async method return a result without heap-allocating a Task when it completes synchronously. The win is one fewer allocation on hot paths that usually finish without awaiting. The cost is a strict await-once contract. Here is what the type actually is, how it works, and the narrow set of cases where it earns its keep.