How To Start Logging With Serilog

Serilog is an easy-to-set-up logging library for .NET with a clear API. In the long list of the Serilog's features you can find:

Support of structured logging, which allows logs to be treated as data sets rather than text.
Compatibility with asynchronous applications and systems.
Multiple logging targets, such as files, console, email, and many other outputs.
Message templates, that helps you to serialize objects using the @ operator

Serilog is useful in the simplest small applications as well as in large and complex ones. Due to its rich configuration abilities, you can use it in all your projects.

In this tutorial you will learn how to:

Create a Console Application project in Visual Studio
Install Serilog and its dependencies
Create and configure the Serilog global logger
Integrate the logger into the C# Console Application

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Prerequisites

You will need:

Windows 10 installed.
Visual Studio installed.

Step 1 — Creating a Project

To get started, you need to create a new project. You can do it in several ways in Visual Studio. The first one is to select Create a new project in Visual Studio start window.

If the Visual Studio IDE is already open, you can follow the path on the top menu bar *File > New > Project *and create a new project this way.

The last way is by using the shortcut: Ctrl + Shift + N.

Step 2 — Installing Dependencies

Before starting to work on the application, you need to install some dependency packages. Visual Studio provides multiple ways to use the NuGet Package Manager. In the tutorial we will use the Package Manager Console.

The first thing you have to do is to open the Package Manager Console. You can do it using Tools > NuGet Package Manager > Package Manager Console. Alternatively, you can sequentially press ALT, V, E, and O.

In the console that opens, run the following commands one by one.

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Install-Package Serilog

Install-Package Serilog.Sinks.Console

Install-Package Serilog.Sinks.File

The Serilog package contains the types. While the Serilog.Sinks namespace includes logging providers, such as Console, Debug, File, HTTP, and others.

Step 3 — Creating a Logger

Now, you are ready to create a logger with the basic configuration.

For the application, we're going to use the Serilog's levels system. The system consists of the 6 levels:

Fatal — used for reporting about errors that are forcing shutdown of the application.
Error — used for logging serious problems occurred during execution of the program.
Warning — used for reporting non-critical unusual behavior.
Information — used for informative messages highlighting the progress of the application for sysadmin and end user.
Debug — used for debugging messages with extended information about application processing.
Verbose — the noisiest level, used for tracing the code.

Default level, if no minimum level is specified, is the information level.

Creating a logger in Serilog is pretty straightforward. You can get the working logger in a few lines.

The following code should be written in the Program.cs file:

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Program.cs
using System;
using Serilog;

namespace SerilogAdvanced
{
    class Program
    {
        static void Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
                            // add console as logging target
                            .WriteTo.Console()
                            // set default minimum level
                            .MinimumLevel.Debug()
                            .CreateLogger();
        }
    }
}

Step 4 — Configuring the Logger

Serilog has rich configuration abilities and provides 2 ways how to configure the logger: programmatically or via a configuration file. You can get advanced information about each of them in the documentation.

In the tutorial we're going to configure the logger programmatically. We've decided to add 2 extra logging targets for the application.

The first logging target is a file for warnings and higher severity logs structured in JSON. Serilog has a built-in JSON formatter which we are going to use in the logger.

The second logging target is a rolling file for all logs. A rolling file is a file used for a certain amount of time. After the rolling interval will pass, the program will automatically create a new file with a date stamp of the creation in the name.

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Program.cs
using System;
using Serilog;
using Serilog.Events;
using Serilog.Formatting.Json;

namespace SerilogAdvanced
{
    class Program
    {
        static void Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
                            // add console as logging target
                            .WriteTo.Console()
                            // add a logging target for warnings and higher severity  logs
                            // structured in JSON format
                            .WriteTo.File(new JsonFormatter(),
                                          "important.json",
                                          restrictedToMinimumLevel: LogEventLevel.Warning)
                            // add a rolling file for all logs
                            .WriteTo.File("all-.logs",
                                          rollingInterval: RollingInterval.Day)
                            // set default minimum level
                            .MinimumLevel.Debug()
                            .CreateLogger();
    }
    }
}

Step 5 — Creating Extra Classes

We're going to use 2 extra classes. To create a new file for a class, you can press CRTL + SHIFT + A and select C# class in the window that opens.

The first file will contain a Person class. You can see its code in the snippet below.

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Person.cs
using Serilog;
using System;

namespace SerilogAdvanced
{
    class Person
    {
        public string Name { get; set; }
        public string LastName { get; set; }

        public Person(string name, string lastName)
        {
            Name = name;
            LastName = lastName;

            Log.Debug("Created a person {@person} at {now}", this, DateTime.Now);
        }
    }
}

The second file will contain a Car class. You can see its code in the snippet below.

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Car.cs
using System;
using Serilog;

namespace SerilogAdvanced
{
    class Car
    {
        public string Model { get; set; }
        public int YearReleased { get; set; }
        public Person Owner { get; set; }

        public Car(string model, int yearReleased, Person owner)
        {
            Model = model;
            YearReleased = yearReleased;
            Owner= owner;

            Log.Debug("Created a car {@person} at {now}", this, DateTime.Now);
        }
    }
}

Also, if you'd like to reduce the byte count of the log events, you may prefer the CompactJsonFormatter instead of the Serilog's default JsonFormatter.

Step 6 — Logging

To demonstrate how the logger works, we will log some simple messages.

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Program.cs
using System;
using Serilog;
using Serilog.Events;
using Serilog.Formatting.Json;

namespace SerilogAdvanced
{
    class Program
    {
        static void Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
                            // add console as logging target
                            .WriteTo.Console()
                            // add a logging target for warnings and higher severity  logs
                            // structured in JSON format
                            .WriteTo.File(new JsonFormatter(), "important.json")
                            // add a rolling file for all logs
                            .WriteTo.File("all.logs",
                                          restrictedToMinimumLevel: LogEventLevel.Warning,
                                          rollingInterval: RollingInterval.Day)
                            // set default minimum level
                            .MinimumLevel.Debug()
                            .CreateLogger();

            // create 2 persons
            var person1 = new Person("Jonh", "Gold");
            var person2 = new Person("James", "Miller");
            // create 2 cars
            var car1 = new Car("Tesla Model S", 2020, person1);
            var car2 = new Car("Tesla Model X", 2020, person2);
        // logging
            Log.Verbose("Some verbose log");
            Log.Debug("Some debug log");
            Log.Information("Person1: {@person}", person1);
            Log.Information("Car2: {@car}", car2);
            Log.Warning("Warning accrued at {now}", DateTime.Now);
            Log.Error("Error accrued at {now}", DateTime.Now);
            Log.Fatal("Problem with car {@car} accrued at {now}", car1, DateTime.Now);
        }
    }
}

Now, let's build and run the program. You can simply do this by pressing CTRL + F5.

After the execution, your console's output should look like:

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Output
[01:08:21 DBG] Created a person {"Name": "Jonh", "LastName": "Gold", "$type": "Person"} at 05/07/2021 01:08:21
[01:08:21 DBG] Created a person {"Name": "James", "LastName": "Miller", "$type": "Person"} at 05/07/2021 01:08:21
[01:08:21 DBG] Created a person {"Model": "Tesla Model S", "YearReleased": 2020, "Owner": {"Name": "Jonh", "LastName": "Gold", "$type": "Person"}, "$type": "Car"} at 05/07/2021 01:08:21
[01:08:21 DBG] Created a person {"Model": "Tesla Model X", "YearReleased": 2020, "Owner": {"Name": "James", "LastName": "Miller", "$type": "Person"}, "$type": "Car"} at 05/07/2021 01:08:21
[01:08:21 DBG] Some debug log
[01:08:21 INF] Person1: {"Name": "Jonh", "LastName": "Gold", "$type": "Person"}
[01:08:21 INF] Car2: {"Model": "Tesla Model X", "YearReleased": 2020, "Owner": {"Name": "James", "LastName": "Miller", "$type": "Person"}, "$type": "Car"}
[01:08:21 WRN] Warning accrued at 05/07/2021 01:08:21
[01:08:21 ERR] Error accrued at 05/07/2021 01:08:21
[01:08:21 FTL] Problem with car {"Model": "Tesla Model S", "YearReleased": 2020, "Owner": {"Name": "Jonh", "LastName": "Gold", "$type": "Person"}, "$type": "Car"} accrued at 05/07/2021 01:08:21

Now, let's check the logs written in the files. The files are located in the same folder as your executable. In our case it is C:\\Users\\username\\source\\repos\\SerilogAdvanced\\SerilogAdvanced\\bin\\Debug\\netcoreapp3.1.

First, your important.json file should look like.

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important.json
{"Timestamp":"2021-05-07T01:08:21.5384429+01:00","Level":"Warning","MessageTemplate":"Warning accrued at {now}","Properties":{"now":"2021-05-07T01:08:21.5380346+01:00"}}
{"Timestamp":"2021-05-07T01:08:21.5778513+01:00","Level":"Error","MessageTemplate":"Error accrued at {now}","Properties":{"now":"2021-05-07T01:08:21.5777435+01:00"}}
{"Timestamp":"2021-05-07T01:08:21.5801829+01:00","Level":"Fatal","MessageTemplate":"Problem with car {@car} accrued at {now}","Properties":{"car":{"_typeTag":"Car","Model":"Tesla Model S","YearReleased":2020,"Owner":{"_typeTag":"Person","Name":"Jonh","LastName":"Gold"}},"now":"2021-05-07T01:08:21.5799493+01:00"}}

Second, the file for all logs will contain the current date. In our case, this is all-20210507.logs.

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all-20210507.logs
2021-05-07 01:08:21.236 +01:00 [DBG] Created a person {"Name":"Jonh","LastName":"Gold","$type":"Person"} at "2021-05-07T01:08:21.2119367+01:00"
2021-05-07 01:08:21.404 +01:00 [DBG] Created a person {"Name":"James","LastName":"Miller","$type":"Person"} at "2021-05-07T01:08:21.4044950+01:00"
2021-05-07 01:08:21.431 +01:00 [DBG] Created a person {"Model":"Tesla Model S","YearReleased":2020,"Owner":{"Name":"Jonh","LastName":"Gold","$type":"Person"},"$type":"Car"} at "2021-05-07T01:08:21.4308327+01:00"
2021-05-07 01:08:21.476 +01:00 [DBG] Created a person {"Model":"Tesla Model X","YearReleased":2020,"Owner":{"Name":"James","LastName":"Miller","$type":"Person"},"$type":"Car"} at "2021-05-07T01:08:21.4768049+01:00"
2021-05-07 01:08:21.513 +01:00 [DBG] Some debug log
2021-05-07 01:08:21.514 +01:00 [INF] Person1: {"Name":"Jonh","LastName":"Gold","$type":"Person"}
2021-05-07 01:08:21.515 +01:00 [INF] Car2: {"Model":"Tesla Model X","YearReleased":2020,"Owner":{"Name":"James","LastName":"Miller","$type":"Person"},"$type":"Car"}
2021-05-07 01:08:21.538 +01:00 [WRN] Warning accrued at "2021-05-07T01:08:21.5380346+01:00"
2021-05-07 01:08:21.577 +01:00 [ERR] Error accrued at "2021-05-07T01:08:21.5777435+01:00"
2021-05-07 01:08:21.580 +01:00 [FTL] Problem with car {"Model":"Tesla Model S","YearReleased":2020,"Owner":{"Name":"Jonh","LastName":"Gold","$type":"Person"},"$type":"Car"} accrued at "2021-05-07T01:08:21.5799493+01:00"

Conclusion

Proper logging can greatly assist in the support and development of your application. This may seem like a daunting task, but Serilog is a fast and configurable logging framework that greatly simplifies the task.

In the tutorial, you have configured your logging system with multiple logging targets for a .NET console application with Serilog.

Now developing and maintaining your .NET applications will be much easier!