I am new to C# and using Task
. I was trying to run this application but my application hangs every time. When I am adding task.wait()
, it keeps waiting and never returns. Any help is much appreciated.
EDIT:
I want to call DownloadString Asynchronously. And when I am doing task.Start() as suggested by "Austin Salonen" I don't get the address of location but default value in location string from returnVal. It means that location got value assigned before task got completed. How can I make sure that after task is completed only then location gets assigned returnVal.
public class ReverseGeoCoding
{
static string baseUri = "http://maps.googleapis.com/maps/api/geocode/xml?latlng={0},{1}&sensor=false";
string location = "default";
static string returnVal = "defaultRet";
string latitude = "51.962146";
string longitude = "7.602304";
public string getLocation()
{
Task task = new Task(() => RetrieveFormatedAddress(latitude, longitude));
//var result = Task.Factory.StartNew(RetrieveFormatedAddress("51.962146", "7.602304"));
task.Wait();
//RetrieveFormatedAddress("51.962146", "7.602304");
location = returnVal;
return location;
}
public static void RetrieveFormatedAddress(string lat, string lng)
{
string requestUri = string.Format(baseUri, lat, lng);
using (WebClient wc = new WebClient())
{
wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
wc.DownloadStringAsync(new Uri(requestUri));
}
}
static void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
var xmlElm = XElement.Parse(e.Result);
var status = (from elm in xmlElm.Descendants()
where elm.Name == "status"
select elm).FirstOrDefault();
if (status.Value.ToLower() == "ok")
{
var res = (from elm in xmlElm.Descendants()
where elm.Name == "formatted_address"
select elm).FirstOrDefault();
//Console.WriteLine(res.Value);
returnVal = res.Value;
}
else
{
returnVal = "No Address Found";
//Console.WriteLine("No Address Found");
}
}
}
Wait is a synchronization method that causes the calling thread to wait until the current task has completed. If the current task has not started execution, the Wait method attempts to remove the task from the scheduler and execute it inline on the current thread.
Wait will synchronously block until the task completes. So the current thread is literally blocked waiting for the task to complete. As a general rule, you should use " async all the way down"; that is, don't block on async code.
You aren't actually running the task. Debugging and checking task.TaskStatus
would show this.
// this should help
task.Start();
// ... or this:
Task.Wait(Task.Factory.StartNew(RetrieveFormatedAddress("51.962146", "7.602304")));
Though if you're blocking, why start another thread to begin with?
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