WebException thrown when locking screen of the Emulator (WindowsPhone8)

Question

I have a webrequest to get a xml.That works great but when i press F12(lock screen) while the the server is requested by my app...I got a WebException.
I use a taskCompeltionSource object...
Here is my code

public async Task<String> Query(DataRequestParam dataRequestParam)
        {

            _dataRequestParam = dataRequestParam;

            try
            {
                Result = "";
                Result = await myDownloadString(dataRequestParam);

            }

            catch (WebException we)//ERROR IS CAUGHT HERE
            {
                throw new WebException(we.Message);

            }
            catch (Exception ex)
            {
                throw new MyException(ex.Message);

            }

            return Result;
        }

        public static Task<string> myDownloadString(DataRequestParam dataRequestParam)
        {
            var tcs = new TaskCompletionSource<string>();
            var web = new WebClient();

            if (!string.IsNullOrEmpty(dataRequestParam.AuthentificationLogin))
            {
                System.Net.NetworkCredential account = new NetworkCredential(dataRequestParam.AuthentificationLogin, dataRequestParam.AuthentificationPassword);
                web.Credentials = account;
            }

                web.DownloadStringCompleted += (s, e) =>
                {
                    if (e.Error != null) tcs.TrySetException(e.Error);
                    else if (e.Cancelled) tcs.TrySetCanceled();
                    else tcs.TrySetResult(e.Result);
                };

                web.DownloadStringAsync(dataRequestParam.TargetUri);
                return tcs.Task;

        }

If you haven't disabled ApplisationIdleDetection, your process is stopped while entering Lock screen - thus you probably get the exception. — Romasz, Mar 03 '14 at 12:05
Thanks i implemented this line : PhoneApplicationService.Current.ApplicationIdleDetectionMode =IdleDetectionMode.Disabled; and it doesn't crash anymore... — Paul Martinez, Mar 03 '14 at 13:16
You should be aware of some more things while using Idle detection and it also want prevent from exception when hitting Start buton (example) - I've added an answer with some links - maybe it will help. — Romasz, Mar 03 '14 at 13:27

Romasz · Accepted Answer · 2014-03-03T13:46:29.443

0

If you haven't disabled ApplisationIdleDetection, your process is stopped while entering Lock screen - thus you probably get the exception - like I've said in comment. Disabling will solve this issue, but you must be aware of few things:

you will still get the exception when hitting Start Button (or other case putting your app to dormant state). In this case your app is stopped and there is no way to prevent this behaviour.
you must fulfill certification requirements when disabling App Idle Detection - point 6.3
if you want to download files in the Background (lock screen, after closing/leaving app) then you can think of Background Transfers

edited Mar 03 '14 at 13:46

answered Mar 03 '14 at 13:25

Romasz

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Thank your for these informations...But in my case I dont need to perform downloads during my app is locked. If Web request are processing all I need is to prevent that the app crashes when it becomes locked...The webrequest can finish or not it doesn't matter... I tested with the start button but it doesn't crash when ApplicationIdleDetectionMode is Disabled then I hitted the back button and i came back in my app while the request was still processing... – Paul Martinez Mar 03 '14 at 14:56

WebException thrown when locking screen of the Emulator (WindowsPhone8)

1 Answers1