Serilog for ASP.NET Core

Using Serilog logging for ASP.NET Core.

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Logging during startup

Use Serilog.Extensions.Hosting for logging framework’s internal operations.

dotnet add package Serilog.Extensions.Hosting

Use CreateBootstrapLogger() for appsettings.json configuration and dependency injection logging

Program.cslink
Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Debug()
    .WriteTo.Console()
    .CreateBootstrapLogger();

try
{
    Log.Information("Starting web application");

    var builder = WebApplication.CreateBuilder(args);

    var app = builder.Build();
    app.UseHsts();
    app.UseStaticFiles();
    app.UseRouting();
    app.MapControllers();

    app.Run();
}
catch (Exception ex)
{
    Log.Fatal(ex, "Application terminated unexpectedly");
}
finally
{
    Log.CloseAndFlush();
}

Add UseSerilog()

Add packages

dotnet add package Serilog.AspNetCore

Add UseSerilog() to the host builder

const string OutputTemplate = "[{Timestamp:HH:mm:ss} {Level:u3}] [{SourceContext}] {Message:lj}{NewLine}{Exception}";

builder.UseSerilog((_, _, cfg) => cfg
    .MinimumLevel.Debug()
    .MinimumLevel.Override("<project_name_space>", LogEventLevel.Warning)
    .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
    .MinimumLevel.Override("Microsoft.Hosting.Lifetime", LogEventLevel.Information)
    .MinimumLevel.Override("System", LogEventLevel.Information)
    .WriteTo.Console(outputTemplate: OutputTemplate)
    .WriteToFile(builderConfiguration.GetValue<string>("LogFolder") ?? string.Empty));

Use {SourceContext} to log the namespace.

Write to different log files by level

To create log by different logEvent, implement methond WriteToFile()

private static LoggerConfiguration WriteToFile(this LoggerConfiguration loggerConfiguration, string logFolder)
{
    var logEventLevels = new[]
    {
        LogEventLevel.Debug,
        LogEventLevel.Information,
        LogEventLevel.Warning,
        LogEventLevel.Error
    };

    foreach (var logEventLevel in logEventLevels)
    {
        loggerConfiguration.WriteTo.Logger(configuration =>
        {
            configuration.Filter.ByIncludingOnly(logEvent => logEvent.Level == logEventLevel)
                .WriteTo.File(path: $"{logFolder}\\{logEventLevel}-.log",
                    outputTemplate: OutputTemplate,
                    rollingInterval: RollingInterval.Day,
                    fileSizeLimitBytes: 1 * 1024 * 1024, // 1MB
                    retainedFileCountLimit: 2,
                    rollOnFileSizeLimit: true,
                    shared: true,
                    flushToDiskInterval: TimeSpan.FromSeconds(1));
        });
    }

    return loggerConfiguration;
}

When setting rollingInterval, the log files will append current date to the file name. e.g: Information-20230101.log

Request logging

Use UseSerilogRequestLogging() for request logging

app.UseSerilogRequestLogging(options =>
{
    // // Emit debug-level events instead of the defaults
    options.GetLevel = (_, _, _) => LogEventLevel.Debug;
    
    // Attach additional properties to the request completion event
    options.EnrichDiagnosticContext = async (diagnosticContext, httpContext) =>
    {
        diagnosticContext.Set("RequestHost", httpContext.Request.Host.Value);
        diagnosticContext.Set("RequestScheme", httpContext.Request.Scheme);
        diagnosticContext.Set("QueryString", httpContext.Request.QueryString);
    
        var requestBody = await GetRequestBody(httpContext.Request);
        diagnosticContext.Set("RequestBody", requestBody);
    };
    
    options.MessageTemplate = 
        "{RequestMethod} {RequestBody}{RequestPath}{QueryString} responded {StatusCode} in {Elapsed:0.0000} ms";
});

Add UseSerilogRequestLogging() in Startup.cs before any handlers whose activities should be logged, by this way can also reduce unnesseray log

// ...
var app = builder.Build();

app.UseSerilogRequestLogging();

app.UseStaticFiles(); // Won't skip static file logs

// ...

Then implement the method for gartering request body

private static async Task<string> GetRequestBody(HttpRequest httpRequest)
{
    string requestBody = string.Empty;

    if (httpRequest.Path.ToString().ContainsAny(nameof(AuthenticateController.Login),
            nameof(AuthenticateController.Registry)))
    {
        requestBody = "[Redacted] Contains Sensitive Information. ";
    }
    else
    {
        using var reader = new HttpRequestStreamReader(httpRequest.Body, Encoding.UTF8);
        var payload = await reader.ReadToEndAsync();
        if (!string.IsNullOrEmpty(payload))
        {
            var json = JsonSerializer.Deserialize<object>(payload);
            requestBody = $"{JsonSerializer.Serialize(json)} ";
        }
    }

    return requestBody;
}

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Serilog.AspNetCore
Serilog : Log to different files - Stack Overflow