using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        string inVal = "-4_Issue 71,-6_Issue 69,";

        var parsed = ParsePhrase(inVal);

        Console.WriteLine($"parsed: {string.Join(",", parsed)}");

    }

    public static List<int> ParsePhrase(string inString){

        Console.WriteLine($"inString: {inString}");

        var outList = new List<int>();

        foreach(var item in inString.Split(',')){

            if(item.IndexOf("_") < 0)

                continue;

            var val = item.Substring(0,item.IndexOf("_"));

            int? valInt = int.TryParse(val, out var outVal)? outVal:null;

            if(valInt != null)

                outList.Add(valInt.Value);

        }

        return outList;

    }

}