using System;
using System.Text.RegularExpressions;
 
namespace RegExApplication
{
   public class Program
   {
      public static void Main(string[] args)
      {
         string input = "x-[ABCD]";
         string pattern = "^x-\\[(.*)\\]$";
         Regex rgx = new Regex(pattern);
 
         Match match = rgx.Match(input);
 
        	if (match.Success)
        	{
            	Console.WriteLine(match.Groups[1].Value);
        	}
      }
   }
}

dXNpbmcgU3lzdGVtOwp1c2luZyBTeXN0ZW0uVGV4dC5SZWd1bGFyRXhwcmVzc2lvbnM7CiAKbmFtZXNwYWNlIFJlZ0V4QXBwbGljYXRpb24KewogICBwdWJsaWMgY2xhc3MgUHJvZ3JhbQogICB7CiAgICAgIHB1YmxpYyBzdGF0aWMgdm9pZCBNYWluKHN0cmluZ1tdIGFyZ3MpCiAgICAgIHsKICAgICAgICAgc3RyaW5nIGlucHV0ID0gIngtW0FCQ0RdIjsKICAgICAgICAgc3RyaW5nIHBhdHRlcm4gPSAiXngtXFxbKC4qKVxcXSQiOwogICAgICAgICBSZWdleCByZ3ggPSBuZXcgUmVnZXgocGF0dGVybik7CiAgICAgICAgIAogICAgICAgICBNYXRjaCBtYXRjaCA9IHJneC5NYXRjaChpbnB1dCk7CgogICAgICAgIAlpZiAobWF0Y2guU3VjY2VzcykKICAgICAgICAJewogICAgICAgICAgICAJQ29uc29sZS5Xcml0ZUxpbmUobWF0Y2guR3JvdXBzWzFdLlZhbHVlKTsKICAgICAgICAJfQogICAgICB9CiAgIH0KfQ==