Calculate distance between two postal codes in miles using C# in ASP.Net

Hi nauna,

Create below class and call it according to your need and refer below links for more details.

Refer below links.

C# Distance Between Two Post Codes

Determine the distance between ZIP codes using C#

Calculating the distance between two Zip Codes in C#

Refer below code.

C#

public static class Distance
{
    // Handy structure for Long/Lat information  
    public struct Coords
    {
        public double Longitude;
        public double Latitude;
    }

    // Unit calculations  
    public enum Units
    {
        Miles,
        Kilometres
    }

    // Will return a null if the Google API is unable to find either post code, or the country constraint fails  
    public static double? BetweenTwoPostCodes(string postcodeA, string postcodeB, string countryCodeWithin, Units units)
    {
        var ll1 = PostCodeToLongLat(postcodeA, countryCodeWithin);
        if (!ll1.HasValue) return null;
        var ll2 = PostCodeToLongLat(postcodeB, countryCodeWithin);
        if (!ll2.HasValue) return null;
        return ll1.Value.DistanceTo(ll2.Value, units);
    }

    // Overload for UK post codes  
    public static double? BetweenTwoUKPostCodes(string postcodeA, string postcodeB)
    {
        return BetweenTwoPostCodes(postcodeA, postcodeB, "GB", Units.Miles);
    }

    // Uses the Google API to resolve a post code (within the specified country)  
    public static Coords? PostCodeToLongLat(string postcode, string countryCodeWithin)
    {
        // Download the XML response from Google  
        var client = new WebClient();
        var encodedPostCode = HttpUtility.UrlEncode(postcode);
        var url = string.Format("http://maps.google.com/maps/geo?q={0}&output=xml", encodedPostCode);
        var xml = client.DownloadString(url);
        var doc = new XmlDocument();
        doc.LoadXml(xml);

        // Create a custom namespace manager  
        var nsmgr = new XmlNamespaceManager(doc.NameTable);
        nsmgr.AddNamespace("ge", "http://earth.google.com/kml/2.0");
        nsmgr.AddNamespace("oa", "urn:oasis:names:tc:ciq:xsdschema:xAL:2.0");

        // Any results?  
        var nodelist = doc.SelectNodes("//ge:kml/ge:Response/ge:Placemark", nsmgr);
        if (nodelist == null || nodelist.Count == 0) return null;

        // Results are already ordered by accuracy, so take the first one  
        var node = nodelist[0];

        // Check the Country constraint  
        var countryname = node.SelectSingleNode("oa:AddressDetails/oa:Country/oa:CountryNameCode", nsmgr);
        if (countryname.FirstChild.Value != countryCodeWithin)
            return null;

        // Get the raw Long/Lat coordinates (I wish there was a nicer way..  
        // perhaps averaging the LongLat enclosing box?)  
        var coords = node.SelectSingleNode("ge:Point/ge:coordinates", nsmgr).FirstChild.Value.Split(',');
        double longitude;
        double lattitude;
        if (!Double.TryParse(coords[0], out longitude)) return null;
        if (!Double.TryParse(coords[1], out lattitude)) return null;

        return new Coords
        {
            Longitude = longitude,
            Latitude = lattitude
        };
    }

    public static double DistanceTo(this Coords from, Coords to, Units units)
    {
        // Haversine Formula...  
        var dLat1InRad = from.Latitude * (Math.PI / 180.0);
        var dLong1InRad = from.Longitude * (Math.PI / 180.0);
        var dLat2InRad = to.Latitude * (Math.PI / 180.0);
        var dLong2InRad = to.Longitude * (Math.PI / 180.0);

        var dLongitude = dLong2InRad - dLong1InRad;
        var dLatitude = dLat2InRad - dLat1InRad;

        // Intermediate result a.  
        var a = Math.Pow(Math.Sin(dLatitude / 2.0), 2.0) +
                Math.Cos(dLat1InRad) * Math.Cos(dLat2InRad) *
                Math.Pow(Math.Sin(dLongitude / 2.0), 2.0);

        // Intermediate result c (great circle distance in Radians).  
        var c = 2.0 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1.0 - a));

        // Unit of measurement  
        var radius = 6371;
        if (units == Units.Miles) radius = 3959;

        return radius * c;
    }
}