Get country name and code based on lat/long c#

Question

The best solution I found so far is,

using Two10.CountryLookup;

var lookup = new ReverseLookup();
try
{   // get country details based on lat/long
    var country = lookup.Lookup(float.Parse(scandata.gpslat), float.Parse(scandata.gpslong));
  string cName = country.name;
   string cCode = country.code;
}
catch(Exception e)
{
    Console.WriteLine("Exception :"+e);
}

But This object is too heavy, I have millions of records to go through. This object making my script slow. is there any other faster method?

Are you creating a new instance of ReverseLookup for every record you want to lookup? — CathalMF, Mar 09 '16 at 17:16
@TheAnathema https://github.com/two10degrees/Two10.CountryLookup — CathalMF, Mar 09 '16 at 17:17
How about using the Google Geocoding API, like [this](http://stackoverflow.com/a/4013635/6017401)? — ChrisS, Mar 09 '16 at 17:24
@ChrisS Hes trying to locate millions of records. Doing a web lookup would be very slow. — CathalMF, Mar 09 '16 at 17:26

CathalMF · Answer 1 · 2016-03-09T17:32:08.963

1

If you read the ReadMe on the website it tells you that the ReverseLookup object creation is expensive. So they want to you to create it once and then reuse it.

https://github.com/vansha/Two10.CountryLookup/blob/master/readme.md

It is expensive because it loads and parses the entire 7.1MB region list in the constructor.

I just ran some tests. Querying 20 locations and creating the ReverseLookup object each time took 10 seconds. Creating it once and reusing it 20 times took .6 seconds. Reusing it 2000 times took 2 seconds.

edited Mar 09 '16 at 17:32

answered Mar 09 '16 at 17:21

CathalMF

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@D4Developer Have a look at The Anathema's solution. Hes created a singleton example which is pretty good. – CathalMF Mar 09 '16 at 17:42

score 1 · Accepted Answer · answered Mar 09 '16 at 17:40

If you read the source code of your library, it loads a region list.

this.Regions = ParseInput(LoadFile()).ToArray();

Even though ParseInput() and LoadFile() have deferred execution on them, it immediately casts the IEnumerable<Region> to an array, which executes it and forces the evaluation on every constructor. It's an expensive operation, so it should be set once.

You should either construct the ReverseLookup item once, or implement it in a Singleton.

public class RegionLocator
{
    private static RegionLocator instance;
    private static ReverseLookup ReverseLookup;

    private RegionLocator() { }

    public static RegionLocator Instance
    {
        get
        {
            if (instance == null)
            {
                instance = new RegionLocator();
                ReverseLookup = new ReverseLookup();
            }
            return instance;
        }
    }

    public Region Lookup(float lat, float lng, RegionType[] types)
    {
        return ReverseLookup.Lookup(lat, lng, types);
    }

    public Region[] Regions()
    {
        return ReverseLookup.Regions;
    }
}

And use as such:

RegionLocator.Instance.Lookup(float.Parse(scandata.gpslat), float.Parse(scandata.gpslong));

Perfect ..:) You made my day .. It was silly to initialize it every time :(. — HirenPatel_, Mar 09 '16 at 17:58
@D4Developer, yep, using the Singleton it took 1.3 seconds to process 5000 sets of lat/lons, and 23 seconds to process 50 sets after initializing it every time. — Frozenthia, Mar 09 '16 at 19:05

Get country name and code based on lat/long c#

2 Answers2