using System;

using YamlDotNet.Serialization;

using YamlDotNet.Serialization.NamingConventions;

public class Program

{

    public static void Main()

    {

        var serializer = new SerializerBuilder()

            .WithQuotingNecessaryStrings()

            .WithNamingConvention(UnderscoredNamingConvention.Instance)

            .ConfigureDefaultValuesHandling(DefaultValuesHandling.OmitNull)

            .Build();

        var model = new Model

        {

            Value1 = "Y",

            Value2 = "no",

            ObjValue = new

            {

                Value1 = "-1",

            },

        };

        var yaml = serializer.Serialize(model);

        Console.WriteLine(yaml);

    }

}

​

public class Model {

    public string Value1 { get; set; }

    public string Value2 { get; set; }

    public object ObjValue { get; set; }

}