# .NET and More > Silverlight >  Silverlight Helloworld service

## ERUM

i have service just hellworld in my application 




```
 [OperationContract]
        public string HelloWorld() 
        {
            return "Helloworld";
        }
```

here is some patch in Reference.cs



```
   public event System.EventHandler<HelloWorldCompletedEventArgs> HelloWorldCompleted;
```




```
   public partial class HelloWorldCompletedEventArgs : System.ComponentModel.AsyncCompletedEventArgs
        {

            private object[] results;

            public HelloWorldCompletedEventArgs(object[] results, System.Exception exception, bool cancelled, object userState) :
                base(exception, cancelled, userState)
            {
                this.results = results;
            }
        }
```

and here is the .xmal page code behind

```
           client.HelloWorldCompleted += new EventHandler<HelloWorldCompletedEventArgs>(Func);
           client.HelloWorldAsync();
```




```
  void Func(object sender, HelloWorldCompletedEventArgs e)
        {
            string s;
         
           
        }
```


it gives me 2 error

Error	1	The type or namespace name 'HelloWorldCompletedEventArgs' could not be found (are you missing a using directive or an assembly reference?)	C:\Users\Iram\Documents\Visual Studio 2008\Projects\SilverlightWithWCFService\SilverlightWithWCFService\MainPage.xaml.cs	30	59	SilverlightWithWCFService


Error	2	'SilverlightWithWCFService.CustomerService.SampleServiceClient' does not contain a definition for 'HelloWorldAsync' and no extension method 'HelloWorldAsync' accepting a first argument of type 'SilverlightWithWCFService.CustomerService.SampleServiceClient' could be found (are you missing a using directive or an assembly reference?)	C:\Users\Iram\Documents\Visual Studio 2008\Projects\SilverlightWithWCFService\SilverlightWithWCFService\MainPage.xaml.cs	31	19	SilverlightWithWCFService


so far i did not find nay thing i m missing  , so please help me,mean while i m looking into the solution of teh problem

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