c# - Need help to write web api wrapper for Silverlight project -

please bear me new silverlight. need write web api wrapper (i've named webclientwrapper) supposed consume rest services. project uses silverlight 5. facing many problems while writing such wrapper. there lot of examples demonstrating rest service consumption in c#. unfortunately none of them worked me. it's been challenge me done need. below requirements:

1) ui should not freeze while make request,

2) calling methods webclientwrapper should easier possible.

3) .net framework version of project should not changed.

i tried following things far:

1) use of httpclient. referred link: http://www.asp.net/web-api/overview/web-api-clients/calling-a-web-api-from-a-net-client. problem approach cannot call readasasync method. calling method requires change in framework (i.e. replacing dlls or changing framework version) not feasible.

2) use of webclient. http://www.kastory.net/index.php?option=com_content&view=article&id=25:rest-web-service-in-c-with-silverlight-and-asp-net-web-api&catid=32:web-services&itemid=130.
problem (not sure!) have make changes in way call methods webclientwrapper. trying accomplish calling method webclientwrapper this:

var appointments = webclientwrapper.get<appointments>(new dictionary<string, string>()         {             {"hospitalid", "19465654546"}         }, "appointment"); 

below code snippet tried in webclientwrapper.

private const string baseurl = "http://localhost:63455/api";      private static webclient getclient()     {         int leadingint = new random().next(10000, 99999);         int trailingint = new random().next(1000, 9999);         string date = datetime.now.tostring("ddhhmmmmssmmyyyyyss");         string ticketstring = string.format("{0}{1}{2}", leadingint, date, trailingint);          var client = new webclient();         client.headers["accept"] = ticketstring;         client.headers["useragent"] = "receptionistapp";          return client;     }      private static void downloadcompletionhandler<t>(object sender, downloadstringcompletedeventargs e)     {         encoding messageencoding = encoding.utf8;         var serializer = new datacontractjsonserializer(typeof (t));         var memorystream = new memorystream(messageencoding.getbytes(e.result));         var objecttoreturn = (t) serializer.readobject(memorystream);     }      public static t get<t>(dictionary<string, string> paramdictionary, string controller)     {         string absoluteurl = baseurl + controller + "?";         absoluteurl = paramdictionary.aggregate(absoluteurl,             (current, keyvaluepair) => current + (keyvaluepair.key + "=" + keyvaluepair.value + "&"));         absoluteurl = absoluteurl.trimend('&');         webclient client = getclient();         client.downloadstringcompleted += downloadcompletionhandler<t>;         client.downloadstringasync(new uri(absoluteurl));     } 

below things want mention regarding code above:

1) obvious, compiler throws error method get<t> since i've not returned object of type t. how shall object downloadstringasync? know can use downloadstringtaskasync. not available current framework. changes have make in code appointments shown in get<appointments> method call?

2) downloadcompletionhandler<t> bound return void want return objecttoreturn shown in code.

help appreciated. new code snippets fulfill requirements welcome.

restsharp helped me instead of webclient.