CSharpEssentials.LoggerHelper.Sink.File 5.2.2

CSharpEssentials.LoggerHelper.Sink.File

Rolling JSON log files with configurable retention and dynamic per-property routing for CSharpEssentials.LoggerHelper.

Targets: net8.0 · net9.0 · net10.0 — Part of the CSharpEssentials.LoggerHelper ecosystem. Install only the sinks you need.

Install

dotnet add package CSharpEssentials.LoggerHelper
dotnet add package CSharpEssentials.LoggerHelper.Sink.File

Quick Setup — JSON

Add to appsettings.json:

{
  "LoggerHelper": {
    "ApplicationName": "MyApp",
    "Routes": [
      { "Sink": "File", "Levels": ["Information", "Warning", "Error", "Fatal"] }
    ],
    "Sinks": {
      "File": {
        "Path": "Logs",
        "RollingInterval": "Day",
        "RetainedFileCountLimit": 14
      }
    }
  }
}

// Program.cs
builder.Services.AddLoggerHelper(builder.Configuration);

var app = builder.Build();
app.UseLoggerHelper();   // ← required: activates sinks and registers middleware

Absolute paths work on both Windows and Linux:

• Windows: "C:\\Logs\\MyApp" or "C:/Logs/MyApp"
• Linux / Docker: "/var/log/myapp" or "logs" (relative to the working directory)

Quick Setup — Fluent API

builder.Services.AddLoggerHelper(b => b
    .WithApplicationName("MyApp")
    .AddRoute("File", LogEventLevel.Information, LogEventLevel.Warning, LogEventLevel.Error, LogEventLevel.Fatal)
    .ConfigureFile(f => {
        f.Path                  = "Logs";
        f.RollingInterval       = "Day";
        f.RetainedFileCountLimit = 14;
    })
);

var app = builder.Build();
app.UseLoggerHelper();   // ← required

What You'll See

Each log event is written as a single JSON line:

{"@t":"2026-06-01T14:23:01.1230000Z","@mt":"Order {OrderId} placed by {UserId}","@l":"Information","OrderId":42,"UserId":"usr_99","ApplicationName":"MyApp","SourceContext":"OrdersController"}

Fields at a glance:

Files are named log-YYYYMMDD.txt by default and roll at midnight.

Dynamic File Routing by Property

Route logs into separate subdirectories based on any runtime property — ideal for multi-tenant apps, per-module separation, or environment-based routing.

JSON config

"Sinks": {
  "File": {
    "Path": "Logs",
    "RollingInterval": "Day",
    "FileNameProperty": "TenantId"
  }
}

How it works

// Logs with TenantId="acme" → Logs/acme/log-20260601.txt
using (_logger.BeginScope(new Dictionary<string, object?> { ["TenantId"] = "acme" }))
{
    _logger.LogInformation("Order processed");
    _logger.LogError("Payment failed");
}

// Logs without TenantId → Logs/log-20260601.txt  (base path, no subdirectory)
_logger.LogInformation("App started");

Fluent API

builder.Services.AddLoggerHelper(b => b
    .AddRoute("File", LogEventLevel.Information, LogEventLevel.Error)
    .ConfigureFile(f => {
        f.Path             = "Logs";
        f.FileNameProperty = "TenantId";
        f.MaxOpenFiles     = 128;   // LRU pool limit for open file handles (default: 64)
    })
);

Configuration Options

All logs are written in structured JSON format using Serilog's JsonFormatter. There is no plain-text mode for this sink — use the Console sink for human-readable output.

Troubleshooting

Links

• Documentation
• CSharpEssentials.LoggerHelper (core)
• GitHub Repository
• MIT License