using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        string input = "This is a test string which could be any text";

        string exclude = "aeiou";

        var stripped = Regex.Replace(input, "[" + exclude +"]", "");

        Console.WriteLine(stripped);

        var cleaned = Regex.Replace(stripped, "[ ]{2,}", " ");

        Console.WriteLine(cleaned);

    }

}