Eine nicht behandelte Ausnahme aufgetreten, wenn ObservableCollection Liste

Question

in Aktualisierung versuchen, Daten aus einem Webservice in eine sfDataGrid Parameter i Suche von Verwendung zu laden OnNavigatedTo

zuerst eine Scheinzeile in das Netz geladen wird, weil ich die Daten erhalten kann nicht OnNavigatedTo noch, dann läuft sie OnNavigatedTo und erhält die Daten von dem Webservice und GOSE in die Daten zu dem ObservableCollection hinzu, dass das Gitter Itemssource auf

gesetzt

using Prism.Commands; 
using Prism.Mvvm; 
using Prism.Navigation; 
using System; 
using System.Collections.Generic; 
using System.Collections.ObjectModel; 
using System.ComponentModel; 
using System.Linq; 

namespace PrismUnityApp2.ViewModels 
{ 

public class HovedsideViewModel : BindableBase, INotifyPropertyChanged , INavigationAware 
{ 
    MobileService.VaksServiceClient ws = new MobileService.VaksServiceClient(); 
    INavigationService _navigationService; 
    public event PropertyChangedEventHandler PropertyChanged; 


    private DateTime selectedDate; 
    public DateTime SelectedDate 
    { 
     get { return selectedDate; } 
     set 
     { 
      if (selectedDate != value) 
      { 
       selectedDate = value; 

       if (PropertyChanged != null) 
       { 
        PropertyChanged(this, 
         new PropertyChangedEventArgs("SelectedDate")); 
       } 
      } 
     } 
    } 

    private DateTime minimumSelectedDate; 
    public DateTime MinimumSelectedDate 
    { 
     get { return minimumSelectedDate; } 
     set 
     { 
      if (minimumSelectedDate != value) 
      { 
       minimumSelectedDate = value; 

       if (PropertyChanged != null) 
       { 
        PropertyChanged(this, 
         new PropertyChangedEventArgs("MinimumSelectedDate")); 
       } 
      } 
     } 
    } 

    public DelegateCommand Navigatetest { get; private set; } 
    public DelegateCommand NavigateToBestilling { get; private set; } 

    public string latitude { get; set; } 
    private string _longitude; 

    public string longitude 
    { 
     get { return _longitude; } 
     set 
     { 
      _longitude = value; 
      ws.GetToemmeDatasAsync(latitude, longitude, DateTime.Today.AddDays(-7)); // needs to be set to the 1 of november as its the only day with data 
     } 
    } 




    public HovedsideViewModel(INavigationService navigationService) 
    { 
     try 
     { 
      toemmeListe = new ObservableCollection<ToemningData>(); 
     } 
     catch (Exception ex) 
     { 

      throw; 
     } 
      SetRowData(); 

     MinimumSelectedDate = DateTime.Now; 
     SelectedDate = DateTime.Now.AddDays(1); 

     _navigationService = navigationService; 
     Navigatetest = new DelegateCommand(Navigate); 
     NavigateToBestilling = new DelegateCommand(_NavigateToBestilling); 
    } 



    private void _NavigateToBestilling() 
    { 
     _navigationService.NavigateAsync("Bestilling"); 
    } 

    private void Navigate() 
    { 
     _navigationService.NavigateAsync("Scanner"); 
    } 

    public void OnNavigatedFrom(NavigationParameters parameters) 
    { 

    } 

    public void OnNavigatedTo(NavigationParameters parameters) 
    { 
     latitude = parameters["lat"].ToString(); // if the phone inst near latitude "55,7070631" and longitude "12,4235393" then remove the part where it gets data from parameters 
     longitude = parameters["lon"].ToString(); // and use the two lines under this 
     //latitude = "55,7070631"; 
     //longitude = "12,4235393"; 
    } 

    public void SetRowData() 
    { 
     ws.GetToemmeDatasCompleted += Ws_GetToemmeDatasCompleted; 
     ws.GetToemmeDatasAsync(latitude, longitude, DateTime.Today.AddDays(-7)); // needs to be set to the 1 of november as its the only day with data 
    } 


    private void Ws_GetToemmeDatasCompleted(object sender, MobileService.GetToemmeDatasCompletedEventArgs e) 
    { 

     int numOfRows = 0; 
     try 
     { 
      numOfRows = e.Result.Count(); // awdawd 
     } 
     catch (Exception) 
     { 
      numOfRows = 0; 
     } 
     //ToemmeListe.Clear(); 
     if (numOfRows > 0) 
     { 
      foreach (var toemming in e.Result) 
      { 
       ToemningData _ToemningData = new ToemningData(); 
       _ToemningData.Fraktion = toemming.Fraktion; 
       _ToemningData.ToemmeID = toemming.ToemmeId; 
       _ToemningData.Type = toemming.type; 
       _ToemningData.Vaegt = toemming.weight; 
       ToemmeListe.Add(_ToemningData); // failes when it trys to add a new row // An unhandled exception occured. 
      } 
     } 
     else // if there isnt any data then set one row saying that there isnt any data 
     { 
      ToemningData _ToemningData = new ToemningData(); 
      _ToemningData.Fraktion = "Igen Data"; 
      _ToemningData.ToemmeID = -1; 
      _ToemningData.Type = "Igen Data"; 
      _ToemningData.Vaegt = "Igen Data"; 
      ToemmeListe.Add(_ToemningData); 
     } 
    } 

    private ObservableCollection<ToemningData> toemmeListe; 

    public ObservableCollection<ToemningData> ToemmeListe 
    { 
     get { return toemmeListe; } 
     set { this.toemmeListe = value; } 
    } 

    } 
} 

XAML

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
      xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms" 
      prism:ViewModelLocator.AutowireViewModel="True" 
      xmlns:sfgrid="clr-namespace:Syncfusion.SfDataGrid.XForms;assembly=Syncfusion.SfDataGrid.XForms" 
      x:Class="PrismUnityApp2.Views.Hovedside" 
      xmlns:sys="clr-namespace:System;assembly=mscorlib" 
      Title="test"> 

    <ContentPage.Content> 

    <Grid> 
     <Grid.RowDefinitions> 
     <RowDefinition Height="20" /> 
     <RowDefinition Height="50"/> 
     <RowDefinition Height="*" /> 
     <RowDefinition Height="50" /> 
     <RowDefinition Height="50" /> 
     </Grid.RowDefinitions> 

     <Grid.ColumnDefinitions> 
     <ColumnDefinition Width="*"/> 
     <ColumnDefinition Width="*"/> 
     <ColumnDefinition Width="*"/> 
     </Grid.ColumnDefinitions> 

     <DatePicker Date="{Binding SelectedDate,Mode=TwoWay}" MinimumDate="{Binding MinimumSelectedDate,Mode=TwoWay}" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="3" HorizontalOptions="Center"> 
     <DatePicker.Format>yyyy-MM-dd</DatePicker.Format> 
     </DatePicker> 



     <sfgrid:SfDataGrid x:Name="dataGrid" 
        AutoGenerateColumns="False" 
        ColumnSizer="Star" 
        SelectedIndex="1" 
        SelectionMode="Single" 
       ItemsSource="{Binding ToemmeListe}" 
        AllowSorting="True" 
          Grid.Row="2" 
          Grid.Column="0" Grid.ColumnSpan="3" 
         > 

     <sfgrid:SfDataGrid.Columns x:TypeArguments="syncfusion:Columns"> 
      <sfgrid:GridTextColumn HeaderText="Fraktion" 
            MappingName="Fraktion" />  <!--Fraktion-->            
      <sfgrid:GridTextColumn HeaderText="Type" 
            MappingName="Type" />   <!--Type--> 
      <sfgrid:GridTextColumn HeaderText="Vaegt" 
            MappingName="Vaegt" />  <!--vægt--> 
     </sfgrid:SfDataGrid.Columns> 

     </sfgrid:SfDataGrid> 

     <Button Text="Scan" FontSize="24" Grid.Row="3" Grid.Column="0" Command="{Binding Navigatetest}"/> 
     <Button Text="Mail" FontSize="24" Grid.Row="3" Grid.Column="2"/> 
     <Button Text="Manuel" FontSize="24" Grid.Row="4" Grid.Column="0" Grid.ColumnSpan="3" HorizontalOptions="Center" Command="{Binding NavigateToBestilling}"/> 

    </Grid> 


    </ContentPage.Content> 

</ContentPage> 

Wenn es in der Ws_GetToemmeDatasCompleted ankommt, nachdem die Daten vom Webservice abgerufen wurden, stoppt es bei ToemmeListe.Add (_ToemningData); in

foreach (var toemming in e.Result) 
      { 
       ToemningData _ToemningData = new ToemningData(); 
       _ToemningData.Fraktion = toemming.Fraktion; 
       _ToemningData.ToemmeID = toemming.ToemmeId; 
       _ToemningData.Type = toemming.type; 
       _ToemningData.Vaegt = toemming.weight; 
       ToemmeListe.Add(_ToemningData); // failes when it trys to add a new row // An unhandled exception occured. 
      } 

und sagt eine nicht behandelte Ausnahme aufgetreten.

Jede Hilfe ist sehr geschätzt

im Visual Studio 2015 Community mit, Xamarin, Prisma V6.2.0 Xam.Plugin.Geolocator V3.0.4 und Syncfusion hauptsächlich es auf einem Sony Xperia Z3 mit Android-Version 6.0 ausgeführt wird. 1 und unter Verwendung API 23

Dropbox link to the full project

Die Lösung i mit

ging

using Prism.Commands; 
using Prism.Mvvm; 
using Prism.Navigation; 
using PrismUnityApp2.ProxyClient; 
using System; 
using System.Collections.Generic; 
using System.Collections.ObjectModel; 
using System.ComponentModel; 
using System.Linq; 
using System.ServiceModel; 
using System.Threading.Tasks; 

namespace PrismUnityApp2.ViewModels 
{ 


    public class HovedsideViewModel : BindableBase, INotifyPropertyChanged, INavigationAware 
    { 
     MobileService.VaksServiceClient ws = new MobileService.VaksServiceClient(); 
     INavigationService _navigationService; 
     public event PropertyChangedEventHandler PropertyChanged; 


     private DateTime selectedDate; 
     public DateTime SelectedDate 
     { 
      get { return selectedDate; } 
      set 
      { 
       if (selectedDate != value) 
       { 
        selectedDate = value; 

        if (PropertyChanged != null) 
        { 
         PropertyChanged(this, 
          new PropertyChangedEventArgs("SelectedDate")); 
        } 
       } 
      } 
     } 

     private DateTime minimumSelectedDate; 
     public DateTime MinimumSelectedDate 
     { 
      get { return minimumSelectedDate; } 
      set 
      { 
       if (minimumSelectedDate != value) 
       { 
        minimumSelectedDate = value; 

        if (PropertyChanged != null) 
        { 
         PropertyChanged(this, 
          new PropertyChangedEventArgs("MinimumSelectedDate")); 
        } 
       } 
      } 
     } 

     public DelegateCommand Navigatetest { get; private set; } 
     public DelegateCommand NavigateToBestilling { get; private set; } 

     public string latitude { get; set; } 
     private string _longitude; 

     public string longitude 
     { 
      get { return _longitude; } 
      set { _longitude = value; } 
     } 




     public HovedsideViewModel(INavigationService navigationService) 
     { 

      SetRowData(); // initialize the grid 

      MinimumSelectedDate = DateTime.Now; // this one will be revmoved later. its fine that they can go back and watch but not edite it 
      SelectedDate = DateTime.Now.AddDays(1); 

      _navigationService = navigationService; 
      Navigatetest = new DelegateCommand(Navigate); 
      NavigateToBestilling = new DelegateCommand(_NavigateToBestilling); 
     } 



     private void _NavigateToBestilling() 
     { 
      _navigationService.NavigateAsync("Bestilling"); 
     } 

     private void Navigate() 
     { 
      _navigationService.NavigateAsync("Scanner"); 
     } 

     public void OnNavigatedFrom(NavigationParameters parameters) 
     { 

     } 

     public async void OnNavigatedTo(NavigationParameters parameters) 
     { 
      Xamarin.Forms.Device.BeginInvokeOnMainThread(async() => 
      { 
       latitude = parameters["lat"].ToString(); // if the phone inst near latitude "55,7070631" and longitude "12,4235393" then remove the part where it gets data from parameters 
       longitude = parameters["lon"].ToString(); // and use the two lines under this 
                  //latitude = "55,7070631"; 
                  //longitude = "12,4235393"; 
       var ggg = await CallService(new MobileService.Toemning { Latitude = latitude, Longitude = longitude, date = new DateTime(2016, 11, 1) }); // the date is set to a day where there is data 
       var justatest = 0; 
       ToemmeListe.Clear(); 
       foreach (var toemming in ggg) 
       { 

        ToemningData _ToemningData = new ToemningData(); 
        _ToemningData.Fraktion = toemming.Fraktion; 
        _ToemningData.ToemmeID = toemming.ToemmeId; 
        _ToemningData.Type = toemming.Type; 
        _ToemningData.Vaegt = toemming.Weight; 
        ToemmeListe.Add(_ToemningData); 
       } 

      }); 

     } 

     MobileService.Toemning ToWCFServiceTodoItem(MobileService.Toemning item) 
     { 
      return new MobileService.Toemning 
      { 
       Fraktion = item.Fraktion, 
       ToemmeId = item.ToemmeId, 
       Type = item.Type, 
       date = item.date, 
       Latitude = item.Latitude, 
       Longitude = item.Longitude, 
       Weight = item.Weight 
      }; 
     } 


     public async Task<ObservableCollection<MobileService.Toemning>> CallService(MobileService.Toemning item) 
     { 
      var todoItem = ToWCFServiceTodoItem(item); 
      MobileService.VaksServiceClient client = new MobileService.VaksServiceClient(new BasicHttpBinding(), new EndpointAddress("http://vf-kssweb2/Vaks2Svc/VaksService.svc?singleWsdl")); 
      var t = Task<ObservableCollection<MobileService.Toemning>>.Factory.FromAsync(
        ((MobileService.IVaksService)client.InnerChannel).BeginGetToemmeDatas, 
        ((MobileService.IVaksService)client.InnerChannel).EndGetToemmeDatas, 
        todoItem, TaskCreationOptions.None); 
      return await t; 
     } 

     public void SetRowData() 
     { 

      try 
      { 
       toemmeListe = new ObservableCollection<ToemningData>(); 
      } 
      catch (Exception ex) 
      { 

       throw; 
      } 

      ToemningData _ToemningData = new ToemningData(); 
      _ToemningData.Fraktion = "Igen Data"; 
      _ToemningData.ToemmeID = -1; 
      _ToemningData.Type = "Igen Data"; 
      _ToemningData.Vaegt = "Igen Data"; 
      ToemmeListe.Add(_ToemningData); 
     } 

     private ObservableCollection<ToemningData> toemmeListe; 

     public ObservableCollection<ToemningData> ToemmeListe 
     { 
      get { return toemmeListe; } 
      set { this.toemmeListe = value; } 
     } 




    } 
} 

Answer 1

Sie dürfen keinen ObservableCollection von einem beliebigen Thread außer dem, der ihn erstellt hat, ändern (normalerweise der UI-Thread). Sie müssen marshall die Add Operationen zu diesem Thread zurück, vorzugsweise async/await mit:

private async Task FillList() 
{ 
    // on the ui thread here... 

    // leaving it to wait for i/o operations or cpu-bound work on a threadpool thread 
    var data = await _server.FetchData(); 

    // here we are back on the ui thread and update the list 
    foreach (var item in data) 
     TransformItemAndAddItToTheList(item); 
}