using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

         string str = "[{name:{buyerfirstname:Randy, buyermiddlename:null, buyerlastname:Johnson}, buyerfullname:Randy Johnson, businessname:null}]";

         showMatch(str, @"(?<=[:,])(.*?)(?=\}[,\]])");

    }

     private static void showMatch(string text, string expr) {

         MatchCollection mc = Regex.Matches(text, expr);

         string[] matches=new string[10000];

         foreach (Match m in mc) {

            string tailored=m.Value.Trim().Replace("{","");

            matches = Regex.Split(tailored, ","); 

            for(int i=0;i<matches.Length;i++)

            {

                Console.WriteLine(matches[i].ToString().Trim());

            }   

         }

      }

}