How to return a value with async WCF service calls?

How to return a value with async WCF service calls?

11-19-2009 10:01 AM |

Hello,

I'm currently trying to get a DataTable created with Silverlight Dataset (www.silverlightdataset.net) from a SQL statement.

I've written a method that allows me to call a WCF service which is executing the statement and getting the result in XML data. 

My silverlight app should convert the XML data to a Datatable and make it usable.

 
        public DataTable getData(string lvsSQL)
        {
            DataTable cvsDT = new DataTable();
            AsyncCallback tmpCallback = new AsyncCallback(delegate(IAsyncResult asyncResult)
            {
                string lvsXML = ((WCFService.IWCFService)asyncResult.AsyncState).EndReturnData(asyncResult);
                DataSet ds = new DataSet();

                ds.FromXml(lvsXML);

                cvsDT = ds.Tables.Count > 0 ? ds.Tables[0] : new DataTable();
                b_IsCompleted = true;
            });

            b_IsCompleted = false;

            IAsyncResult asResult = serviceClient.BeginReturnData(lvsSQL, tmpCallback, serviceClient);

            return cvsDT;
        }
 

 That was my first try but that didn't work. My cvsDT is empty because the procedure is asynchronous and he returns before the statement is executed. When I'm using AsyncWaitHandle.WaitOne() the debugger says the Thread died and nothing happens.

I don't know how to do this. All I want to do is to fill a combo box directly with a SQL statement.

Does anyone of you have a solution?

I'm not able to use LINQ2SQL or the Entitiy Framework because we need dynamic database / table usage without entities and untypized Datasets to get our data from.

Regards

Re: How to return a value with async WCF service calls?

11-19-2009 10:10 AM |

Hi,

You need to subscribe to serviceClient.ReturnDataCompleted(maybe name is different it is depend on method to call) event and you will get data at that handler.

Re: Re: How to return a value with async WCF service calls?

11-19-2009 10:25 AM |

 Hi,

 yes, that's working. But I won't get a result value for my function after that. Just in the result parameter.

I'm using a Channel Factory. Is it possible to get Completed Events as Channel Factory user, too?

Regards

Re: Re: How to return a value with async WCF service calls?

11-19-2009 10:48 AM |

Seuche:

Is it possible to get Completed Events as Channel Factory user, too?

No, need to use calbacks. Did you see http://www.netfxharmonics.com/2008/11/Understanding-WCF-Services-in-Silverlight-2?

Seems like all right at code which you show. Look at that article there are a part about Channel Factory.

Re: Re: How to return a value with async WCF service calls?

11-19-2009 4:46 PM |

 Hi,

my problem is that I'm just getting a empty datatable because the return statement is being executed before  the EndGetData() is executed. I don't get anywhere with this problem. Everything works except that.

Regards

Re: Re: Re: How to return a value with async WCF service calls?

11-20-2009 7:39 PM |

 Is there really no way to wrap a Begin / End Pattern into one function to return the result of the End method with just passing the parameter?

Re: Re: How to return a value with async WCF service calls?

11-27-2009 3:08 PM |

I've got a simular problem. Could you tell me how you implemented the wrapper begin/end?

Re: Re: Re: How to return a value with async WCF service calls?

12-03-2009 11:42 AM |

 Hello,

 follow this link: CodeProject: Synchronous Web Service Calls with Silverlight: Dispelling the async-only myth. Free source code and programming help