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Using Rx to Geocode an Address in Bing Maps

I am studying the use of Rx extensions for the Silverlight 4 application that I am working on. I created an example application to nail the process, and I cannot get it to return anything. Here is the main code:

    private IObservable<Location> GetGPSCoordinates(string Address1)
    {
        var gsc = new GeocodeServiceClient("BasicHttpBinding_IGeocodeService") as IGeocodeService;

        Location returnLocation = new Location();
        GeocodeResponse gcResp = new GeocodeResponse();

        GeocodeRequest gcr = new GeocodeRequest();
        gcr.Credentials = new Credentials();
        gcr.Credentials.ApplicationId = APP_ID2;
        gcr.Query = Address1;

        var myFunc = Observable.FromAsyncPattern<GeocodeRequest, GeocodeResponse>(gsc.BeginGeocode, gsc.EndGeocode);
        gcResp = myFunc(gcr) as GeocodeResponse;

        if (gcResp.Results.Count > 0 && gcResp.Results[0].Locations.Count > 0)
        {
            returnLocation = gcResp.Results[0].Locations[0];
        }
        return returnLocation as IObservable<Location>;
    }

gcResp is returned as null. Any thoughts or suggestions would be greatly appreciated.

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3 answers

Richard (and others),

So, I have the code that returns the location, and I have the code of the calling code. Here is (hopefully) the final release. When I call GetGPSCoordinates, the next statement runs immediately, without waiting for the subscription to complete. Here is an example in the OnClick event handler.

Location newLoc = new Location();

GetGPSCoordinates(this.Input.Text).ObserveOnDispatcher().Subscribe(x =>
            {
             if (x.Results.Count > 0 && x.Results[0].Locations.Count > 0)
                  {
                     newLoc = x.Results[0].Locations[0];
                     Output.Text = "Latitude: " + newLoc.Latitude.ToString() +
  ", Longtude: " + newLoc.Longitude.ToString();
                  }
             else
                  {
                    Output.Text = "Invalid address";
                  }
});
            Output.Text = " Outside of subscribe --- Latitude: " + newLoc.Latitude.ToString() +
  ", Longtude: " + newLoc.Longitude.ToString();

Output.Text, , , .

- , , Foreach. Rx Extensions , async . , , .

, , ?

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, , , . .

, :

private IObservable<Location> GetGPSCoordinates(string Address1)
{
    IGeocodeService gsc = 
        new GeocodeServiceClient("BasicHttpBinding_IGeocodeService");

    Location returnLocation = new Location();
    GeocodeResponse gcResp  = new GeocodeResponse();

    GeocodeRequest gcr = new GeocodeRequest();
    gcr.Credentials = new Credentials();
    gcr.Credentials.ApplicationId = APP_ID2;
    gcr.Query = Address1;

    var factory = Observable.FromAsyncPattern<GeocodeRequest, GeocodeResponse>(
        gsc.BeginGeocode, gsc.EndGeocode);

    return factory(gcr)
        .Where(response => response.Results.Count > 0 && 
                           response.Results[0].Locations.Count > 0)
        .Select(response => response.Results[0].Locations[0]);
}

( ), .Take(1) Where Select.

:. , , , OnError, . , , SelectMany:

return factory(gcr)
    .SelectMany(response => (response.Results.Count > 0 && 
        response.Results[0].Locations.Count > 0)
        ? Observable.Return(response.Results[0].Locations[0])
        : Observable.Throw<Location>(new AddressNotFoundException())
    );
+1

myFunc, , Func<GeocodeRequest, IObservable<GeocodeResponse>>.

Func<GeocodeRequest, IObservable<GeocodeResponse>> myFunc =
    Observable.FromAsyncPattern<GeocodeRequest, GeocodeResponse>
        (gsc.BeginGeocode, gsc.EndGeocode);

, myFunc(gcr), IObservable<GeocodeResponse>, GeocodeResponse. myFunc(gcr) as GeocodeResponse null, .

, , . .Last() . .Subscribe(...), .

:

gcResp = myFunc(gcr).Last();

, .

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