Question

My code is to generate random cordinates of lat and long within a bound:

        Random lastLat = new Random();

        Random lastLon = new Random();

        for (int i = 0; i < 50; i++)
        {
            int lat = lastLat.Next(516400146, 630304598); //18.51640014679267 - 18.630304598192915

            int lon = lastLon.Next(224464416, 341194152); //-72.34119415283203 - -72.2244644165039

            SamplePostData d0 = new SamplePostData();
            d0.Location = new Location(Convert.ToDouble("18." + lat), Convert.ToDouble("-72." + lon));
            AddPushpin(d0);

        }

My output looks like this:
http://img263.imageshack.us/img263/7504/capturerkv.png http://img263.imageshack.us/img263/7504/capturerkv.png

Is there something wrong with how my numbers are generated?

Answer 1

Jørn’s answer gave the problem, but not the solution: just use a single instance of Random:

Random rng = new Random();

for (int i = 0; i < 50; i++)
{
    int lat = rng.Next(516400146, 630304598);
    int lon = rng.Next(224464416, 341194152);
    SamplePostData d0 = new SamplePostData();
    d0.Location = new Location(18d + lat / 1000000000d,
                               -72d - lon / 1000000000d);
    AddPushpin(d0);
}

(I’ve changed the way of using the result, too – there’s no need to convert to and from a string to achieve what you want. An alternative would be to call Random.NextDouble instead and multiply it by the size of the desired range, then add a base value.)

If you’re calling routine multiple times, you should probably use a single instance of Random across those multiple calls. Beware though: Random in .NET is not thread-safe. Ideally you should have a single instance per thread. See my article on randomness for more details of how to handle Random.