using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

public class Test
{
    public class SAPItem
    {
        public string AddressLine1 { set; get; }
        public string FiveDigitZip { set; get; }
        public double? Latitude { set; get; }
        public double? Longitude { set; get; }
        public string MDM_Latitude { set; get; }
        public string MDM_Longitude { set; get; }
    }

    public class MapPoint
    {
        public double Latitude { set; get; }
        public double Longitude { set; get; }
    }

    static List<SAPItem> SAPItems = new List<SAPItem>
    {
        new SAPItem
        {
            AddressLine1 = "Address 1",
            FiveDigitZip = "12345"
        },

        new SAPItem
        {
            AddressLine1 = "Address 2",
            FiveDigitZip = "67890"
        }
    };

    public static void Main(string[] args)
    {
        PullInfo();
    }

    public static void PullInfo()
    {
        // Create tasks to update items with latitude and longitude
        var tasks
            = SAPItems.Where(item => item.Latitude == null || item.Longitude == null)
                .Select(item =>
                    GetMapPoint(item.AddressLine1 + " " + item.FiveDigitZip)
                        .ContinueWith(pointTask => {
                            item.MDM_Latitude = pointTask.Result.Latitude.ToString();
                            item.MDM_Longitude = pointTask.Result.Longitude.ToString();
                        }));

        // Wait for tasks completion (it will block the current thread)
        Task.WaitAll(tasks.ToArray());

        // Iterate to append Lat and Long
        foreach (var item in SAPItems)
            Console.WriteLine(item.MDM_Latitude + " " + item.MDM_Longitude);
    }

    private static Task<MapPoint> GetMapPoint(string add)
    {
        return Task.FromResult(new MapPoint { Latitude = 1, Longitude = 1 });
    }
}