using System;

using System.Text;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var number = new NumberBuilder();

        Console.WriteLine(number

            .WithTexts(new[] {"test", "test2"})

            .WithNumber(10)

            .WithTexts(new[] {"test3"})

            .Build());

    }

}

​

public abstract class Builder<TBuilder> where TBuilder : Builder<TBuilder>

{

    private List<string> texts = new();

    public void AddString(string text) => texts.Add(text);

    public string Build() => string.Join(" ", texts);

    public TBuilder WithTexts(params string[] texts)

    {

        foreach (var text in texts) AddString(text);

        return (TBuilder)this;

    }

}

​

public class NumberBuilder : Builder<NumberBuilder>

{

    public NumberBuilder WithNumber(int number) => WithTexts(number.ToString());

}

​

public class StaticBuilder : Builder<StaticBuilder>

{

    public StaticBuilder WithStatic() => WithTexts("test");

}

​