/// <summary>
/// Deserialize the json zip/coord mapping file into a dictionary object
/// </summary>
/// <returns>ZipCodeDictionary zipCodes</returns>
private static ZipCodeDictionary LoadDictionary()
{
// - Get the context object for the current HTTP request and map the physical filepath to the
// relative filepath (the relative filepath is specified in the Web.config).
// - Read the json file using StreamReader.
// - Deserialize the json data into a ZipCodeDictionary object.
string locZipFilePath = HttpContext.Current.Server.MapPath(_zipFilePath);
try
{
using (StreamReader r = new StreamReader(locZipFilePath))
{
string json = r.ReadToEnd();
ZipCodeDictionary zipCodes = JsonConvert.DeserializeObject <ZipCodeDictionary>(json);
return(zipCodes);
}
}
catch (FileNotFoundException ex)
{
log.ErrorFormat("LoadDictionary(): Path {0} not found.", ex, locZipFilePath);
return(null);
}
catch (Exception ex)
{
log.ErrorFormat("LoadDictionary(): Failed to read dictionary file on path {0}", ex, locZipFilePath);
return(null);
}
}
/// <summary>
/// Static constructor - initializes ZipCodeDictionary object
/// A static class constructor is gauranteed to be called first and only once.
/// </summary>
static ZipCodeGeoLookup()
{
_zipFilePath = ConfigurationManager.AppSettings["ZipCodesJsonMap"];
log = LogManager.GetLogger(typeof(ZipCodeGeoLookup));
zipCodeDictionary = LoadDictionary();
WatchDictionaryFile();
}
/// <summary>
/// Locking method to safely handle file removal after the initial load
/// </summary>
static void GuaranteeData()
{
Object lockObject = new Object();
if (zipCodeDictionary == null)
{
lock (lockObject)
{
if (zipCodeDictionary == null)
{
zipCodeDictionary = LoadDictionary();
}
}
}
}
/// <summary>
/// Check against the dictionary of zipcodes and return a ZipCodeGeoEntry object
/// if a match is found.
/// </summary>
/// <param name="zipCodeEntry">5-digit zip code string</param>
/// <returns>ZipCodeGeoEntry or null if no match</returns>
public GeoLocation GetZipCodeGeoEntry(string zipCodeEntry)
{
GuaranteeData(); // Guarantee we have data before trying to load it.
ZipCodeDictionary zipDict = zipCodeDictionary;
if (zipDict != null && zipDict.ContainsKey(zipCodeEntry))
{
ZipCodeGeoEntry zip = zipDict[zipCodeEntry];
return(new GeoLocation(zip.Latitude, zip.Longitude));
}
else
{
return(null);
}
}
/// <summary>
/// Event handler for .json file in the Configuration\files directory being modified or created.
/// Loads the dictionary again upon file update and logs modify/create event.
/// </summary>
/// <param name="src">event source (not used)</param>
/// <param name="e">event arguments (not used)</param>
private static void OnChange(object src, FileSystemEventArgs e)
{
zipCodeDictionary = LoadDictionary();
log.Warn("OnChange(): Dictionary file was updated.");
}
