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347 posts · Page 15 of 35

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 microsoft-agent-framework ai-agents azure-ai-foundry

How to Deploy a Microsoft Agent Framework Agent to Foundry Hosted Agents

A step-by-step guide to taking a Microsoft Agent Framework agent from your laptop to a managed Foundry Hosted Agent: the C# host code, the azd deploy flow, identity, scaling, and the gotchas that bite in preview.

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 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.

2026-06-21 dotnet efcore csharp

How to seed data with UseSeeding and UseAsyncSeeding in EF Core 11

Seed reference data the right way in EF Core 11 with UseSeeding and UseAsyncSeeding: where to configure them, when they run, the idempotency check you cannot skip, and why you must implement both.

2026-06-21 dotnet efcore csharp

How to seed a many-to-many relationship in EF Core 11

Seed the join table of a many-to-many relationship in EF Core 11: the implicit shadow keys you must name yourself, the UsingEntity HasData pattern, and the runtime UseSeeding alternative that works with skip navigations.