Working with YAML in C# (.NET) | YamlDotNet

Working with YAML in C# (.NET): YamlDotNet Library

YAML (YAML Ain't Markup Language) is a convenient data serialization format often used for configuration files, CI/CD pipeline descriptions, Docker Compose and Kubernetes manifests. In the .NET ecosystem, the primary library for working with YAML is YamlDotNet — a powerful, high-performance tool fully compatible with the YAML 1.1 and 1.2 specifications.

In this article, we will cover: how to install YamlDotNet, perform basic serialization and deserialization of C# objects, configure custom tags, and handle complex data structures.

Installing YamlDotNet

The library is available via NuGet. Run the command in the package manager console:

dotnet add package YamlDotNet

Or via Package Manager Console:

Install-Package YamlDotNet

Basic Usage: Deserializing YAML into a C# Object

Suppose we have a YAML file config.yaml with application settings:

app:  name: MyApp  version: 2.0.1  debug: truedatabase:  host: localhost  port: 5432  credentials:    user: admin    password: secret

Let's create the corresponding C# classes:

public class AppConfig{    public string Name { get; set; }    public string Version { get; set; }    public bool Debug { get; set; }}

public class DatabaseConfig{    public string Host { get; set; }    public int Port { get; set; }    public CredentialsConfig Credentials { get; set; }}

public class CredentialsConfig{    public string User { get; set; }    public string Password { get; set; }}

public class RootConfig{    public AppConfig App { get; set; }    public DatabaseConfig Database { get; set; }}

Now let's deserialize the YAML into an object:

using YamlDotNet.Serialization;using YamlDotNet.Serialization.NamingConventions;

var yamlContent = File.ReadAllText("config.yaml");

var deserializer = new DeserializerBuilder()    .WithNamingConvention(UnderscoredNamingConvention.Instance) // for snake_case    .Build();

var config = deserializer.Deserialize<RootConfig>(yamlContent);

Console.WriteLine(config.App.Name);        // MyAppConsole.WriteLine(config.Database.Port);   // 5432

Serializing C# Objects to YAML

The reverse task — converting a C# object into a YAML string:

var config = new RootConfig{    App = new AppConfig { Name = "MyApp", Version = "2.0.1", Debug = true },    Database = new DatabaseConfig    {        Host = "localhost",        Port = 5432,        Credentials = new CredentialsConfig { User = "admin", Password = "secret" }    }};

var serializer = new SerializerBuilder()    .WithNamingConvention(CamelCaseNamingConvention.Instance) // camelCase in YAML    .Build();

var yaml = serializer.Serialize(config);Console.WriteLine(yaml);

Result:

app:  name: MyApp  version: 2.0.1  debug: truedatabase:  host: localhost  port: 5432  credentials:    user: admin    password: secret

Working with Collections and Complex Types

YamlDotNet fully supports lists, dictionaries, and nested structures. Example with a list:

public class Project{    public string Name { get; set; }    public List<string> Tags { get; set; }}

// YAML:// name: MyProject// tags://   - dotnet//   - yaml//   - csharp

var yaml = @"name: MyProjecttags:  - dotnet  - yaml  - csharp";

var deserializer = new DeserializerBuilder().Build();var project = deserializer.Deserialize<Project>(yaml);

foreach (var tag in project.Tags)    Console.WriteLine(tag);