using System;
using System.Text.RegularExpressions;
using System.IO;
public class Test
{
	public static void Main()
	{
		var searchString = "to find";
		var pattern = @"\b" + searchString + @"\b";    //searchString is passed in.
		Regex rgx = new Regex(pattern);
		var sentence = "I need to find a string in this sentence!";
		Match match = rgx.Match(sentence);
		if (match.Success)
		{
    		Console.WriteLine(match.Value);
		}
	}
	
}