WebClient.OpenReadCompleted - how to wait for this event to finish

Question

So basiacally, I'm creating a dll project which have to get some info from the bing maps api. Below I'm pasting a method which is resposible for getting and serializing the response:

private void GetResponse(Uri uri, Action<Response> callback)
    {
        WebClient wc = new WebClient();
        wc.OpenReadCompleted += (o, a) =>
        {
            if (callback != null)
            {
                DataContractJsonSerializer responseSerializer = new DataContractJsonSerializer(typeof(Response));
                callback(responseSerializer.ReadObject(a.Result) as Response);
            }
        };
        wc.OpenReadAsync(uri);
    }

Below method is using GetResponse method to get lattitudes:

public Lattitudes getLattitudes()
    {
        Lattitudes lattitudes = new Lattitudes();
        GetResponse(geocodeRequestURI, (x) =>
        {
            lattitudes.SouthLatitude = x.ResourceSets[0].Resources[0].BoundingBox[0];
            lattitudes.SouthLatitude = x.ResourceSets[0].Resources[0].BoundingBox[1];
            lattitudes.SouthLatitude = x.ResourceSets[0].Resources[0].BoundingBox[2];
            lattitudes.SouthLatitude = x.ResourceSets[0].Resources[0].BoundingBox[3];
        });
        return lattitudes;
    }

My problem is that second method is returning empty object and part inside GetResponse method is being executed later. Is There a way to wait for this event to finish and then return, or maybe I need to redesign it ?(max version of .NET I can use is 4.0)

Pranay Rana · Answer 1 · 2015-05-12T12:10:27.703

3

I suggest if you want to wait than make use of Task by converting method competable with async and await like as below

private async Task RequestDataAsync(string uri, Action<string> action)
{
    var client = new WebClient();
    string data = await client.OpenReadAsync(uri);
    action(data);
}

call method from the code

   Task t = RequestDataAsync(parameter)
   t.Wait();

this help more : http://www.dotnetperls.com/async

edited May 12 '15 at 12:10

answered May 12 '15 at 12:01

Pranay Rana

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Sounds like solution. Will try – MajkeloDev May 12 '15 at 12:03
"Cannot find all types required by the 'async' modifier. Are you targeting the wrong framework version, or missing a reference to an assembly?" – MajkeloDev May 12 '15 at 12:08
Oh that's it - I can use 4.0 as the highest framework. Anyway thank You for Your help. – MajkeloDev May 12 '15 at 12:12
@MajkeloDev - i m not sure but if you can able to change framework version it will work – Pranay Rana May 12 '15 at 12:15
Problem is that I can't. – MajkeloDev May 12 '15 at 12:17
1

@MajkeloDev - check this http://stackoverflow.com/questions/19423251/in-net-4-0-i-have-not-avaliable-the-async-await-keywords which says you can include by installing some nuget pkg – Pranay Rana May 12 '15 at 12:19

WebClient.OpenReadCompleted - how to wait for this event to finish

1 Answers1