/// <summary>
/// Get a forecast for the given latitude and longitude
/// </summary>
public void GetForecast(string latitude, string longitude)
{
// form the URI
UriBuilder fullUri = new UriBuilder("http://forecast.weather.gov/MapClick.php");
fullUri.Query = "lat=" + latitude + "&lon=" + longitude + "&FcstType=dwml";
// initialize a new WebRequest
HttpWebRequest forecastRequest = (HttpWebRequest)WebRequest.Create(fullUri.Uri);
// set up the state object for the async request
ForecastUpdateState forecastState = new ForecastUpdateState();
forecastState.AsyncRequest = forecastRequest;
// start the asynchronous request
forecastRequest.BeginGetResponse(new AsyncCallback(HandleForecastResponse),
forecastState);
}
/// <summary>
/// Handle the information returned from the async request
/// </summary>
/// <param name="asyncResult"></param>
private void HandleForecastResponse(IAsyncResult asyncResult)
{
// get the state information
ForecastUpdateState forecastState = (ForecastUpdateState)asyncResult.AsyncState;
HttpWebRequest forecastRequest = (HttpWebRequest)forecastState.AsyncRequest;
// end the async request
forecastState.AsyncResponse = (HttpWebResponse)forecastRequest.EndGetResponse(asyncResult);
Stream streamResult;
string newCredit = "";
string newCityName = "";
int newHeight = 0;
// create a temp collection for the new forecast information for each
// time period
ObservableCollection <ForecastPeriod> newForecastList =
new ObservableCollection <ForecastPeriod>();
try
{
// get the stream containing the response from the async call
streamResult = forecastState.AsyncResponse.GetResponseStream();
// load the XML
XElement xmlWeather = XElement.Load(streamResult);
// start parsing the XML. You can see what the XML looks like by
// browsing to:
// http://forecast.weather.gov/MapClick.php?lat=44.52160&lon=-87.98980&FcstType=dwml
// find the source element and retrieve the credit information
XElement xmlCurrent = xmlWeather.Descendants("source").First();
newCredit = (string)(xmlCurrent.Element("credit"));
// find the source element and retrieve the city and elevation information
xmlCurrent = xmlWeather.Descendants("location").First();
newCityName = (string)(xmlCurrent.Element("city"));
newHeight = (int)(xmlCurrent.Element("height"));
// find the first time layout element
xmlCurrent = xmlWeather.Descendants("time-layout").First();
int timeIndex = 1;
// search through the time layout elements until you find a node
// contains at least 12 time periods of information. Other nodes can be ignored
while (xmlCurrent.Elements("start-valid-time").Count() < 12)
{
xmlCurrent = xmlWeather.Descendants("time-layout").ElementAt(timeIndex);
timeIndex++;
}
ForecastPeriod newPeriod;
// For each time period element, create a new forecast object and store
// the time period name.
// Time periods vary depending on the time of day the data is fetched.
// You may get "Today", "Tonight", "Monday", "Monday Night", etc
// or you may get "Tonight", "Monday", "Monday Night", etc
// or you may get "This Afternoon", "Tonight", "Monday", "Monday Night", etc
foreach (XElement curElement in xmlCurrent.Elements("start-valid-time"))
{
try
{
newPeriod = new ForecastPeriod();
newPeriod.TimeName = (string)(curElement.Attribute("period-name"));
newForecastList.Add(newPeriod);
}
catch (FormatException)
{
}
}
// now read in the weather data for each time period
GetMinMaxTemperatures(xmlWeather, newForecastList);
GetChancePrecipitation(xmlWeather, newForecastList);
GetCurrentConditions(xmlWeather, newForecastList);
GetWeatherIcon(xmlWeather, newForecastList);
GetTextForecast(xmlWeather, newForecastList);
// copy the data over
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
// copy forecast object over
Credit = newCredit;
Height = newHeight;
CityName = newCityName;
ForecastList.Clear();
// copy the list of forecast time periods over
foreach (ForecastPeriod forecastPeriod in newForecastList)
{
ForecastList.Add(forecastPeriod);
}
});
}
catch (FormatException)
{
// there was some kind of error processing the response from the web
// additional error handling would normally be added here
return;
}
}
