using System;

public class Program {

    public static void Main() {

        var codigo = new BBCodes(BBCodes.Bold);

        Console.WriteLine(codigo.Wrap("StackOverflow"));

    }

}

​

public sealed class BBCodes {

    public static readonly string Bold = "b";

    public static readonly string Italic = "i";

    //...

    private string code;

    public BBCodes(string code) => this.code = code;

    public string Wrap(string contents) => $"[{code}]{contents}[/{code}]";

}