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Tag: csharp

279 posts · Page 16 of 28

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 dotnet ai-agents agent-framework

Microsoft Agent Framework workflows now survive process restarts via the Durable Task stack

Wrap an Agent Framework Workflow in Microsoft.Agents.AI.DurableTask and each executor step is checkpointed. Crash, redeploy, restart - the run continues where it stopped.

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.

2026-05-06 dotnet ai-agents agent-framework

Microsoft Agent Framework gates risky tool calls behind FunctionApprovalRequestContent

Wrap an AIFunction in ApprovalRequiredAIFunction and the agent stops mid-run to ask permission. Here is how the request and response flow works in C#.

2026-05-06 ai-agents semantic-kernel llm

How to Run a Semantic Kernel Plugin From a BackgroundService

Wire a Microsoft.SemanticKernel 1.75.0 plugin into a hosted BackgroundService on .NET 11 and invoke its KernelFunctions on a PeriodicTimer schedule. Covers DI scopes, [KernelFunction] resolution, prompt-cache-friendly invocation, cancellation, and the lifetime gotchas that bite when you move a plugin off the request path.

2026-05-05 errors csharp dotnet

Fix: System.InvalidOperationException: No connection string named 'DefaultConnection' could be found

If GetConnectionString returns null in .NET 11, your appsettings.json is missing the key, not copied to the build output, or the wrong environment file is being selected. Three checks fix 95% of cases.

2026-05-05 mcp ai-agents ef-core

How to Expose an EF Core Database to an AI Agent via MCP

Wire an EF Core 10 DbContext into a Model Context Protocol server so Claude Code, Cursor, or any compliant client can run safe, scoped queries against your database. Covers IDbContextFactory lifetime, read-only projections, schema discovery tools, AsNoTracking, parameterised filters, row-level scoping, and the destructive-tool gates you need before letting an agent touch UPDATE.