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.
Tag: csharp
217 posts · Page 10 of 22
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.
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.
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.
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#.
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.
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.
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.
How to convert T[] to ReadOnlyMemory<T> in C# (implicit operator and explicit constructor)
Three ways to wrap a T[] in a ReadOnlyMemory<T> in .NET 11: the implicit conversion, the explicit constructor, and AsMemory(). When each is the right call.
How to Add Tool Calling to a Microsoft.Extensions.AI Chat Client
Wire AIFunctionFactory.Create, ChatOptions.Tools, and ChatClientBuilder.UseFunctionInvocation in Microsoft.Extensions.AI 10.5 so an IChatClient can call your .NET methods automatically. Covers OpenAI and Azure OpenAI providers, the FunctionInvokingChatClient knobs that actually matter (iteration limits, concurrent calls, approval prompts, error handling), and streaming responses with tools.