MvvmLight IDataService與異步等待

Question

我試圖找到一種乾淨的方式來完成異步/等待MvvmLight的IDataService模式。

最初我使用回調Action方法來工作類似於模板，但不更新UI。

public interface IDataService 
{ 
    void GetData(Action<DataItem, Exception> callback); 
    void GetLocationAsync(Action<Geoposition, Exception> callback); 
} 

public class DataService : IDataService 
{ 
    public void GetData(Action<DataItem, Exception> callback) 
    { 
     // Use this to connect to the actual data service 

     var item = new DataItem("Location App"); 
     callback(item, null); 
    } 

    public async void GetLocationAsync(Action<Geoposition, Exception> callback) 
    { 
     Windows.Devices.Geolocation.Geolocator locator = new Windows.Devices.Geolocation.Geolocator(); 
     var location = await locator.GetGeopositionAsync(); 
     callback(location, null); 
    } 
} 

public class MainViewModel : ViewModelBase 
{ 
    private readonly IDataService _dataService; 

    private string _locationString = string.Empty; 
    public string LocationString 
    { 
     get 
     { 
      return _locationString; 
     } 

     set 
     { 
      if (_locationString == value) 
      { 
       return; 
      } 

      _locationString = value; 
      RaisePropertyChanged(LocationString); 
     } 
    } 

    /// <summary> 
    /// Initializes a new instance of the MainViewModel class. 
    /// </summary> 
    public MainViewModel(IDataService dataService) 
    { 
     _dataService = dataService; 
     _dataService.GetLocation(
      (location, error) => 
      { 
       LocationString = string.Format("({0}, {1})", 
       location.Coordinate.Latitude, 
       location.Coordinate.Longitude); 
      }); 
    } 
} 

我試圖對數據綁定的GPS座標，但由於異步火災不會在主線程中運行它不會更新UI。

Answer 1

可能是不相關的，但AFAICT你錯過一些報價

 RaisePropertyChanged(LocationString); 

您傳遞改變，而不是它的價值屬性的名稱。