using System;

using System.Text.RegularExpressions;

using System.Text.Json;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        List<dynamic> Out = new List<dynamic>();

        List<string> patternGroups = new List<string> { @"\d{1,}", "D", @"\d{1,}" };

        string pattern  = String.Join("", patternGroups.Select(x => $"({x})"));

        string str = "2D3";

        var r = new Regex(pattern);

        Match match = r.Match(str);

        if (match.Success)

        {           

            for (int i = 0; i < patternGroups.Count; i++)

            {

                Out.Add(new 

                        { 

                            Regex = patternGroups[i], 

                            Value = match.Groups[i + 1].Value 

                        });

            }

        }

        Console.WriteLine(JsonSerializer.Serialize(Out, new JsonSerializerOptions { WriteIndented = true }));   

    }

}