HTTPClient fails on metered connection and working fine on wifi [closed]

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My app works fine with WiFi but when it is over 3G connection it crashes.

here is the code:

protected override async void OnNavigatedTo(NavigationEventArgs e)
{
    if (!App.ViewModel.IsDataLoaded)
    {
        await App.ViewModel.LoadDataAsync();
        DataContext = App.ViewModel;
    }
}

Code for LoadDataAsync

    public async Task<bool> LoadDataAsync()
    {
        Uri uri = new Uri("http://www.28cinema.az/eng/");
        HttpClient client = new HttpClient();
        HtmlDocument htmlDocument = new HtmlDocument();
        HtmlNode htmlNode = new HtmlNode(0, htmlDocument, 1);
        MovieGroup data = new MovieGroup();
        string HtmlResult;    
        HtmlResult = await client.GetStringAsync(uri);
        data.Title = "Today";
        htmlDocument.LoadHtml(HtmlResult);            
        htmlNode = htmlDocument.DocumentNode.SelectSingleNode("//div[@class='poster_wrapper']");

        for (var i = 0; i < (htmlNode.ChildNodes.Count); i++)
        {
            data.Items.Add(new MovieData
            {
                DetailsUrl = htmlNode.SelectSingleNode("div[" + (i + 1) + "]/div[1]/div[1]/a[1]").GetAttributeValue("href", ""),
                Title = htmlNode.SelectSingleNode("div[" + (i + 1) + "]/div[1]/div[1]/a[1]").InnerText,
                Poster = htmlNode.SelectSingleNode("div[" + (i + 1) + "]/img").GetAttributeValue("src", "No poster"),
                Cinema = "28 Cinema"
            });
        }
        Today = data;        
        IsDataLoaded = true;
        return true;
    }

Exception message : No network connection and A task was canceled.

Stack Trace :

   at Cineman.ViewModels.MovieModel.<CreateTodayGroupAsync>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Cineman.ViewModels.MovieModel.<LoadDataAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Cineman.MainPage.<OnNavigatedTo>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__0(Object state)

Any suggestions will be appreciated.

UPD: further looking revealed this line in local variables during breakpoint: 'htmlNode.InnerHtml' threw an exception of type 'System.NullReferenceException'

Answer 1

Well it resolved when I restarted Visual Studio. Weird!

Answer 2

As you discovered, if you attempt to do an HTTP request while there is no network connection, it will throw an exception.

I recommend that you handle the exception, e.g., with a try/catch. How you display the exception details to the user is up to you.