Regular Expression Basics C# Book

using System;
using System.Text.RegularExpressions;
class Program
{
static void Main(string[] args)
{
string r =
@"(?i)\b" +
@"[0-9a-fA-F]{8}\-" +
@"[0-9a-fA-F]{4}\-" +
@"[0-9a-fA-F]{4}\-" +
@"[0-9a-fA-F]{4}\-" +
@"[0-9a-fA-F]{12}" +
@"\b";

string text = "Its key is {11250410-fFff-ffD3-fA0C-0f0fEffCff01}.";
Console.WriteLine (Regex.Match (text, r).Index);
}
}
The output:
12