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CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using System.Text.RegularExpressions;

namespace ConsoleApp16
{
    public class Program
    {
        public static void Main(string[] args)
        {
           var reg = new Regex("(?<=STRING ).*?(?= END)");
           var matched = reg.Matches("This is STRING a222 END, and this is STRING b2838 END, STRING a123 END.");

           foreach(var m in matched)
           {
               Console.WriteLine(m.ToString());
           }
			
        }
	}
}