Table of Contents

File logging

The MADE.Diagnostics.Logging.FileEventLogger writes structured log entries to files on disk. It supports five severity levels, automatic daily log file rotation, and configurable output paths.

Setting up the logger

using MADE.Diagnostics.Logging;

var logger = new FileEventLogger();

By default, logs are written to a Logs folder in the application's root directory, with files named Log-20260517.txt (one file per day).

Customizing the log location

// Change the folder name (relative to app root)
logger.LogsFolderName = "AppLogs";

// Change the file name format (must include {0} for the DateTime parameter)
logger.LogFileNameFormat = "MyApp-{0:yyyyMMdd}.txt";

// Or set a fully custom path
logger.LogPath = @"C:\Logs\MyApp\custom-log.txt";

Writing log entries

The logger provides methods for five severity levels, each with three overloads:

// String message
await logger.WriteInfo("Application started successfully.");

// String message with exception
await logger.WriteError("Failed to process order.", exception);

// Exception only
await logger.WriteCritical(exception);

All severity levels

Method When to use
WriteDebug Detailed diagnostic information for development and troubleshooting.
WriteInfo General operational events (startup, shutdown, configuration loaded).
WriteWarning Unexpected situations that don't prevent operation but should be investigated.
WriteError Errors that affect a specific operation but don't crash the application.
WriteCritical Severe errors that may cause the application to stop functioning.

Log output format

Each entry is written as a tab-separated line with a timestamp, level, correlation ID, and message:

4/6/2021 8:58:40 AM	Level: Info	Id: 230b8802-4ba5-465d-bfdf-433698628673	Message: 'Application diagnostics initialized.'
4/6/2021 8:58:41 AM	Level: Error	Id: f04134e3-7a06-4688-832f-e1e4567aa6e4	Message: 'Error: 'System.InvalidOperationException: Could not complete delete action''

The correlation ID is unique per log entry and can be used to reference specific events from other systems (e.g., AppDiagnostics).

Using the IEventLogger interface

FileEventLogger implements IEventLogger, which you can use for dependency injection and testing:

public class OrderService
{
    private readonly IEventLogger logger;

    public OrderService(IEventLogger logger)
    {
        this.logger = logger;
    }

    public async Task ProcessOrderAsync(Order order)
    {
        await logger.WriteInfo($"Processing order {order.Id}");

        try
        {
            // Process the order
        }
        catch (Exception ex)
        {
            await logger.WriteError($"Failed to process order {order.Id}", ex);
            throw;
        }
    }
}

Note: All IEventLogger methods return Task. Make sure to await them to ensure log entries are flushed to disk.

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