using static System.Console;

using System.Text;

using System.Linq;

public class Program {

    public static void Main() {

        var texto = "(99) 9999-9999";

        WriteLine(texto.Replace("", '(', ')', '-', ' '));

    }

}

​

public static class StringExt {

    public static string Replace(this string str, string newValue, params char[] chars) {

        var sb = new StringBuilder();

        foreach (var chr in str) {

            if (!chars.Contains(chr)) sb.Append(chr);

            else sb.Append(newValue);

        }

        return sb.ToString();

    }

}

​