using System;

using System.Text.RegularExpressions;                   

​

public class Program

{

    public static void Main()

    {

        var regex = new Regex("(?i)seacost");

        Console.WriteLine("{0}", regex.IsMatch("seacost"));

        Console.WriteLine("{0}", regex.IsMatch("Seacost"));

        Console.WriteLine("{0}", regex.IsMatch("SEACOST"));

        Console.WriteLine("{0}", regex.IsMatch("Wat"));

    }

}