This is a code snippet from a 'gecode' class I wrote in C#. This is the portion that retrieves the longitude and latitude for either a postal code or an address of some sort. The function retrieves the co-ordinates via a web request (WebRequest) to geocoder.ca. The response from geocoder.ca is then loaded into an XmlDocument, and parsed.

This code is meant to be integrated into a proximity search engine, to enable people to search for businesses by distance. But you could build it into your Windows applications as well. In my case, I built this into a geocoder class, and then created read-only properties for the longitude/latitude.

protected decimal longitude;
protected decimal lattitude;
protected string url = "http://geocoder.ca/?geoit=XML&";
protected string postalCode;
protected string address;

// your code to set postal code or address here
// check for valid format of postal code

public bool GetGeocode()
    if (postalCode != null)
    {
        url += "postal=" + postalCode;
    }
    else
    {
        // no postal code, so look up based on street
        url += "locate=" +  address;
    }

    WebResponse response;
    try
    {
        WebRequest request = WebRequest.Create(new Uri(url));
        response = request.GetResponse();
    }
    catch (Exception e)
    {
        errorMessage = "website unavailable";
        return false;
    }
    XmlTextReader xmlResponse = new XmlTextReader(response.GetResponseStream());
    XmlDocument xmldoc = new XmlDocument();
    xmldoc.Load(xmlResponse);
    XmlNode LattNode = xmldoc.SelectSingleNode("geodata/latt");
    XmlNode LongNode = xmldoc.SelectSingleNode("geodata/longt");

    if (LattNode == null || LongNode == null)
    {
        errorMessage = "could not parse co-ordinates, check geocode data format";
        return false;
    }

    if (LattNode.InnerText == "")
    {
        errorMessage = "could not retrieve co-ordinates for this address";
        return false;
    }
    else
    {
        resp = LongNode.InnerText;
        longitude = Convert.ToDecimal(LongNode.InnerText);
        lattitude = Convert.ToDecimal(LattNode.InnerText);
        return true;
    }
}