在.NET项目中使用Serilog和Seq自定义日志级别是否可行？

Absolutely! You can totally create custom log levels in Serilog and use that clean, method-style syntax you're asking about. Here's a step-by-step breakdown to make it work:

1. Define Custom Level Extensions for ILogger #

First, create a static class to hold extension methods for ILogger. This is where you'll define your custom log level method(s), mapping them to a custom LogEventLevel value (since Serilog's built-in LogEventLevel is an enum, you can use integer values beyond the default 0-5 range for new levels):

public static class CustomLoggerExtensions
{
    // Define a custom log level (using an integer outside the default 0-5 range)
    private const LogEventLevel MyCustomLevel = (LogEventLevel)6;

    // Basic overload for messages without exceptions
    public static void MyCustomLogLevel(this ILogger logger, string messageTemplate, params object[] args)
    {
        logger.Write(MyCustomLevel, messageTemplate, args);
    }

    // Overload for messages with attached exceptions
    public static void MyCustomLogLevel(this ILogger logger, Exception exception, string messageTemplate, params object[] args)
    {
        logger.Write(MyCustomLevel, exception, messageTemplate, args);
    }
}

2. Configure Serilog to Show Friendly Custom Level Names #

By default, Serilog will display the integer value of your custom level in outputs. To make it show a human-readable name (like "MYCUSTOM" instead of "6"), add an enricher to map the level to a friendly label:

public class CustomLevelEnricher : ILogEventEnricher
{
    public void Enrich(LogEvent logEvent, ILogEventPropertyFactory propertyFactory)
    {
        string levelName = logEvent.Level switch
        {
            (LogEventLevel)6 => "MYCUSTOM",
            // Add mappings for other custom levels if you need them
            _ => logEvent.Level.ToString()
        };

        logEvent.AddPropertyIfAbsent(propertyFactory.CreateProperty("CustomLevel", levelName));
    }
}

Then update your Serilog configuration to use this enricher, and adjust your output templates to use {CustomLevel} instead of the default {Level}:

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Verbose() // Ensure your custom level is included in logging
    .Enrich.With<CustomLevelEnricher>() // Attach the custom level name enricher
    .WriteTo.Console(
        outputTemplate: "[{Timestamp:HH:mm:ss} {CustomLevel}] {Message:lj}{NewLine}{Exception}")
    .WriteTo.Seq("http://localhost:5341") // Seq will recognize the CustomLevel property automatically
    .CreateLogger();

3. Use Your Custom Log Level #

Now you can use your custom method exactly how you wanted! Just make sure to include the namespace of your CustomLoggerExtensions class in your controller:

using YourAppNamespace.CustomLogging;

public class MyController : Controller
{
    private static readonly ILogger Logger = Log.ForContext<MyController>();

    public IActionResult ProcessRequest()
    {
        // Call your custom log level method
        Logger.MyCustomLogLevel("Starting processing for request {RequestId}", HttpContext.TraceIdentifier);

        // Or with an exception
        try
        {
            // Perform a risky operation
        }
        catch (Exception ex)
        {
            Logger.MyCustomLogLevel(ex, "Failed to process request {RequestId}", HttpContext.TraceIdentifier);
        }

        return Ok();
    }
}

Quick Notes #

• If you just need an alias for an existing level (e.g., renaming Warning to Alert), simplify the extension method to call the built-in level directly (e.g., logger.Warning(messageTemplate, args)).
• Seq will let you filter, search, and create alerts using your CustomLevel property just like you would with built-in levels.
• Double-check your minimum log level setting to ensure it's low enough to include your custom level (using Verbose ensures all levels are captured).

内容的提问来源于stack exchange，提问作者Régis NIOX