net core logging to file

Question

How to log exceptions to file

Rajesh Gami · Answer

Logging to a file in .NET Core can be achieved using various methods, including built-in options and popular third-party libraries. 1. Using Built-in .NET Core Logging (without third-party libraries): While ASP.NET Core doesn't include a direct file logging provider out of the box, you can implement a custom ILoggerProvider and ILogger to achieve this. Here's a simplified example of how you might structure such an implementation: Code // FileLogger.cs using Microsoft.Extensions.Logging; using System; using System.IO; public class FileLogger : ILogger { private string filePath; private static object _lock = new object(); public FileLogger(string path) { filePath = path; } public IDisposable BeginScope (TState state) => null; public bool IsEnabled(LogLevel logLevel) => true; // Log all levels public void Log (LogLevel logLevel, EventId eventId, TState state, Exception exception, Func formatter) { if (formatter != null) { lock (_lock) { string fullFilePath = Path.Combine(filePath, DateTime.Now.ToString("yyyy-MM-dd") + "_log.txt"); string logEntry = $"{logLevel}: {DateTime.Now} {formatter(state, exception)}{Environment.NewLine}"; if (exception != null) { logEntry += $"{exception.GetType()}: {exception.Message}{Environment.NewLine}{exception.StackTrace}{Environment.NewLine}"; } File.AppendAllText(fullFilePath, logEntry); } } } } // FileLoggerProvider.cs using Microsoft.Extensions.Logging; public class FileLoggerProvider : ILoggerProvider { private string path; public FileLoggerProvider(string _path) { path = _path; } public ILogger CreateLogger(string categoryName) => new FileLogger(path); public void Dispose() { } } // Program.cs (or Startup.cs in ASP.NET Core) using Microsoft.Extensions.Logging; using System; public class Program { public static void Main(string[] args) { var loggerFactory = LoggerFactory.Create(builder => { builder.AddProvider(new FileLoggerProvider("Logs")); // Specify your log directory builder.AddConsole(); // Optional: also log to console }); var logger = loggerFactory.CreateLogger (); logger.LogInformation("This is an information message."); logger.LogError(new Exception("Something went wrong!"), "This is an error message."); Console.ReadLine(); } } 2. Using Third-Party Logging Libraries (Recommended for Production): Libraries like Serilog or NLog offer more robust and configurable file logging solutions with features like rolling file appenders, custom formatting, and performance optimizations. Example using Serilog: Install NuGet packages. Code dotnet add package Serilog.AspNetCore dotnet add package Serilog.Sinks.File Configure Serilog in Program.cs (or Startup.cs ): Code // Program.cs using Serilog; using Microsoft.Extensions.Hosting; public class Program { public static void Main(string[] args) { Log.Logger = new LoggerConfiguration() .MinimumLevel.Information() .WriteTo.Console() .WriteTo.File("logs/myapp.log", rollingInterval: RollingInterval.Day) .CreateLogger(); try { CreateHostBuilder(args).Build().Run(); } finally { Log.CloseAndFlush(); } } public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .UseSerilog() // Integrate Serilog .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup (); }); } Inject ILogger in your classes. Code using Microsoft.Extensions.Logging; public class MyService { private readonly ILogger _logger; public MyService(ILogger logger) { _logger = logger; } public void DoSomething() { _logger.LogInformation("Doing something important."); } }

Pankajkumar Patel · Answer

Following articles may help: Add File Logging to an ASP.NET Core MVC Application https://www.c-sharpcorner.com/article/add-file-logging-to-an-asp-net-core-mvc-application/ Logging in .NET Core with NLog https://www.c-sharpcorner.com/article/logging-in-net-core-with-nlog/ Implementing Logging in ASP.NET Core MVC using Serilog https://www.c-sharpcorner.com/blogs/implementing-logging-in-asp-net-core-mvc-using-serilog

eggy car · Answer

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