Start Debugging

EN

Daily notes on .NET, C#, EF Core, MAUI, Blazor, and Flutter - for developers who ship.

Start here › Tags Archive

2026-10-11 csharp dotnet

How to tail a log file in C# while another process is still writing to it

Open the log with FileShare.ReadWrite | FileShare.Delete, seek to the end, poll for new bytes, decode them with your own UTF-8 Decoder instead of StreamReader, and handle truncation and rotation explicitly. A tested tail -F implementation for .NET 10 and .NET 11.

2026-10-26 dotnet csharp

How to use a different Serilog output template per log level from appsettings.json

outputTemplate is fixed per sink, so per-level formatting needs either an ExpressionTemplate with {#if @l ...} blocks or two Logger sub-loggers with ByIncludingOnly / ByExcluding filters. Both configured purely from appsettings.json, tested on Serilog 4.4, Serilog.Settings.Configuration 10.0.1 and Serilog.Expressions 5.0.

2026-10-04 dotnet dotnet-10

How to detect Windows session lock, unlock, logon and logoff events in a C# app

Use SystemEvents.SessionSwitch in a desktop or console app, override OnSessionChange in a Windows service, or hook WM_WTSSESSION_CHANGE yourself. Covers .NET 10 code for all three, the hidden '.NET System Events' thread, why services see logon but desktop apps do not, out-of-order notifications, and how to query the current lock state with WTSQuerySessionInformation.

2026-11-10 microsoft-agent-framework dotnet ai-agents

Agent Framework 1.28: A2A Hosting Returns Messages Only, and A2AAgent Takes an Options Object

Microsoft Agent Framework for .NET 1.28.0 removes A2AServerRegistrationOptions.AgentRunMode, so hosted A2A agents always answer with a message, and replaces the id/name/description overloads on A2AAgent and AsAIAgent with A2AAgentOptions. Here is what breaks and how to migrate.

2026-11-10 aspnetcore kestrel http2

How to accept HTTP/2 over cleartext (h2c) in Kestrel behind nginx on .NET 10

Kestrel on .NET 10 only speaks h2c on an endpoint set to HttpProtocols.Http2, and only to clients that use prior knowledge. Http1AndHttp2 without TLS silently falls back to HTTP/1.1, Upgrade: h2c is ignored, and nginx needs proxy_http_version 2 (1.29.4+, stable 1.30) or grpc_pass to talk HTTP/2 upstream. Checked with curl and HttpClient on ASP.NET Core 10.0.10.

2026-11-10 llm ai-agents anthropic-sdk

How to Find Out Why a Claude API Prompt Cache Missed With the diagnostics Request Object

Send diagnostics.previous_message_id on every Messages API call and Claude tells you which part of the prompt broke the cache: model_changed, system_changed, tools_changed or messages_changed, plus an estimate of the tokens you paid to rewrite. Request and response shapes, the pending and not-found states, streaming, a logging helper for anthropic 2.7.0, and the limits.

2026-11-10 aspnetcore dependency-injection async

How to initialize interdependent async singletons at startup in ASP.NET Core

Give each singleton a memoized InitializeAsync that awaits its own dependencies, then await them all from IHostedLifecycleService.StartingAsync. Registration order stops mattering, Kestrel does not accept requests until init finishes, and a failure stops the host. Compared against init before app.Run, IHostedService.StartAsync, and a BackgroundService with a readiness check on ASP.NET Core 10.0.10.

2026-11-10 blazor aspnetcore dotnet-10

How to Run JS Interop on an Element That Was Just Rendered Conditionally in Blazor

Blazor has no nextTick(), but you can build one: a TaskCompletionSource completed in OnAfterRenderAsync. Here is why the @ref is null or stale right after you flip an @if, which common workarounds fail, and a NextRenderAsync helper verified on .NET 10 in both InteractiveServer and InteractiveWebAssembly.

2026-11-09 llm ai-agents anthropic-sdk

How to Add or Change a Tool Mid-Conversation Without Invalidating the Claude Prompt Cache

Stop editing the tools array between turns. Append a role: system message with tool_addition and tool_removal blocks (beta inline-tools-2026-09-15) so a Claude agent gains, loses or re-versions tools while the cached prefix and preserved thinking stay valid. Placement rules, defer_loading, schema changes, error codes and model support.

2026-11-09 dotnet dotnet-10 dotnet-8

.NET 8 and .NET 9 Reach End of Support on November 10, 2026: What Changes Tomorrow

.NET 8 (LTS) and .NET 9 (STS) both leave support on November 10, 2026. What stops, what keeps running, why the two end on the same day, and the minimal steps to move a project to .NET 10.

2026-11-09 csharp dotnet dotnet-10

How to make UseForwardedHeaders work behind nginx in Docker on .NET 10

Behind nginx and Docker, ASP.NET Core's ForwardedHeadersMiddleware silently ignores X-Forwarded-For and X-Forwarded-Proto unless the connecting proxy is in KnownIPNetworks or KnownProxies, and ForwardLimit decides how many hops it walks. The four silent-ignore rules, the KnownNetworks to KnownIPNetworks change in .NET 10, and a runnable repro checked on .NET 10.0.10.

2026-11-09 dotnet msbuild dotnet-cli

How to show MSBuild Exec output in dotnet build with the terminal logger

Why the output of an MSBuild Exec task disappears from dotnet build and dotnet restore since .NET 9, why StandardOutputImportance="High" does not bring it back, and the fixes that do: -tlp:verbosity=detailed, Directory.Build.rsp, -tl:off, and promoting lines to warnings. Checked on SDK 10.0.302 and 11.0.100 RC3.

2026-11-09 csharp dotnet dotnet-11

How to skip empty string properties when serializing with System.Text.Json

System.Text.Json has no WhenWritingEmpty option, WhenWritingDefault still writes "", and a JsonConverter<string> that writes nothing produces invalid JSON. The fix is a type-info resolver modifier that sets JsonPropertyInfo.ShouldSerialize, for reflection and source-generated contexts, checked on .NET 10.0.10 and .NET 11 RC3.

Page 1 of 114 Next ›