How to synchronous in Silvelight Application when call WebService?

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Hi everyone,

Example, I have a Silverlight Application here:

VB

Public data as String = "abc"
Private Sub From_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
  Me.InitControl()
    
  Me.Label1.Text = data
End Sub

Private Sub InitControl()
  AddHandler services.ExeMethodCompleted, AddressOf ExeMethodComplete
  services.ExeMethodAsync(....)
End Sub

Private Sub ExeMethodComplete(ByVal sender As Object, ByVal e As ExeMethodCompletedEventArgs)
  If e.Error Is Nothing Then
    Me.data = e.Result.Nodes(1).Descendants("result").Value
    ''assume return result is Now.ToString()
    '' Me.data = Now.ToString()<code></code>
  End If
End Sub

Result:
Label1's caption is "abc" when expect result is Now.ToString().

Reason:
In Silverlight, call WebServices process is an asynchronous process.

How to synchronous in Silvelight Application when call WebService?

Thanks for helping me.

Posted 25-Jan-11 22:08pm

khuong_vnt

Updated 25-Jan-11 22:11pm

JF2015

v2

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Abhinav S · Answer 1 · 2011-01-27T06:13:00

Solution 2

SIlverlight does not support synchronous calls.

Make use of the Action delegate to come back to your main code once the service returns.

Posted 27-Jan-11 6:13am

Abhinav S

#realJSOP · Answer 2 · 2011-01-27T06:18:00

Solution 3

I wrote an article about how I handle the asynchronous nature of Silverlight:

How I Optimized my Silverlight Asynchronous Web Service Consumption[^]

Posted 27-Jan-11 6:18am

#realJSOP

Espen Harlinn · Answer 3 · 2011-01-27T07:26:00

One option, that might be possible, is to use:
IAsyncResult.AsyncWaitHandle[^] - the asynch web/wcf request methods returns an IAsyncResult.

It's possible that this can be used to create a synchronized wrapper for the service reference. I haven't tried doing things this way in SilverLight, but it seems like an option.

If it works, it can certainly speed up development of "prototypes" for SL.

Regards
Espen Harlinn

lmoelleb · Answer 4 · 2011-01-27T05:03:00

Silverlight only supports async calls. You have to deal with it.

A userinterface is typically databound (on top of a ViewModel), so when you set the data in the Model, the ViewModel will detect the changes, and raise it's own property changed notification that will update the view.

You need to get some books (or find online tutorials etc) on the Model/View/ViewModel pattern. I recommend staying away from toolkits until you understand the pattern and how to implement it manually. If not, experience tells me you end up using the features the toolkit provide for advanced cases for the simple things as well - leaving you with a mess that's hard to maintain.

If you only make extremely simple programs you can just update the label directly in the callback, but do not go down this route if you want to do anything even slightly serious.

How to synchronous in Silvelight Application when call WebService?

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