Populating AutoCompleteTextbox via WCF Service Asynchronously in Silverlight

Step 8: Now set AutoCompleteViaService.Web as startup project and press CTLR + F5. It will launch blank AutoCompleteViaServiceTestPage.html

Step 9: Go to AutoCompleteViaService and click on Service and add service reference.

Step 10: Add service reference window will pop-up. Click on Discover to search any existing service in the solution. You will find that CountryAutoComplete.svc is an available service at this address.
http://localhost:1592/CountryAutoComplete.svc

Give it the name CountryAutoReference.



Step 11: Now we have service reference in out client project which is AutoCompleteViaService.

Open main.xaml.cs , and add service refeence in code behind

using AutoCompleteViaService.CountryAutoReference;

Step 12: In main.xaml , create a textbox as like below

<StackPanel x:Name="LayoutRoot">
<input:AutoCompleteBox x:Name="autoCountry" Margin="10" HorizontalAlignment="Left" Width="200"
Populating="autoCountry_Populating" FilterMode="None">
</input:AutoCompleteBox>

<TextBlock x:Name="lblStatus" Margin="10"></TextBlock>
</StackPanel>

The Populating event fires whenever the AutoCompleteBox is ready to search for results. By default, this happens every time the user presses a key and changes the current text entry.

When the Populating event fires, you have two choices: set the ItemsSource property immediately or launch an asynchronous process to do it. Setting the ItemsSource property immediately makes sense if you have the list of suggestions on hand or you can generate them quickly. The list of suggestions will then appear in the drop-down list right away.

But in many situations, you'll need a potentially time-consuming step to get the list of suggestions, such as performing a series of calculations or querying a web service. In this situation, you need to launch an asynchronous process.

Step 13: So now we will write handler for autoCountry_Populating.

Note : When using an asynchronous operation, you need to explicitly cancel the normal processing in the Populating event handler, by setting PopulatingEventArgs.Cancel to true. You can then launch the asynchronous operation. Following is code which will get the suggestion list asynchronously from a web service.

private void autoCountry_Populating(object sender, System.Windows.Controls.PopulatingEventArgs e)
{
// Signal that the task is being performed asynchronously.
e.Cancel = true;

// Create the web service object.
CountryAutoCompleteClient service = new CountryAutoCompleteClient();

// Make sure the dyanmic URL is set (for testing).

EndpointAddress address = new EndpointAddress("http://localhost:" +
HtmlPage.Document.DocumentUri.Port + "/CountryAutoComplete.svc");
service.Endpoint.Address = address;

// Attach an event handler to the completion event.
service.GetCountryMatchesCompleted += new EventHandler<GetCountryMatchesCompletedEventArgs(service_GetCountryMatchesCompleted);

// Call the web service (asynchronously).
service.GetCountryMatchesAsync(e.Parameter);
lblStatus.Text = "Calling web service ...";

}

To check for correct endpoint adddress, open ServiceReferences.ClientConfig and check the address

<configuration>
<system.serviceModel>
<bindings>
<customBinding>
<binding name="CustomBinding_CountryAutoComplete">
<textMessageEncoding messageVersion="Default" writeEncoding="utf-8" />
<httpTransport maxReceivedMessageSize="2147483647" maxBufferSize="2147483647"
/>
</binding>
</customBinding>
</bindings>
<client>
<endpoint address="http://localhost:1592/CountryAutoComplete.svc"
binding="customBinding" bindingConfiguration="CustomBinding_CountryAutoComplete"
contract="CountryAutoReference.CountryAutoComplete" name="CustomBinding_CountryAutoComplete" />
</client>
</system.serviceModel>

</configuration>

Step 14: On the web server, the code in a GetCountryMatches () web method runs and retrieves the matches:

[OperationContract]
public string[] GetCountryMatches(string inputText)
{
// Get the country (for example, from a server-side database).
Country[] Countries = GetCountry();

// Create a collection of matches.
List<string> countryMatches = new List<string>();
foreach (Country country in Countries)
{
// See if this is a match.
if ((country.countryname.StartsWith(inputText)) ||
(country.countrycode.Contains(inputText)))
countryMatches.Add(country.countryname);
}

return countryMatches.ToArray();
}

private Country[] GetCountry()
{
return new Country[]
{
new Country("Australia","111_AUS"),
new Country("America","222_US"),
new Country("Somalia","333_SOM"),
new Country("South Arfica","444_SA"),
};
}

Step 15: When the asynchronous operation finishes and we receive the result in our Silverlight application, we fill the ItemsSource property with the list of suggestions. Then, we must call the PopulateComplete() method to notify the AutoCompleteBox that the new data has arrived. Here's the callback handler that does the job;

void service_GetCountryMatchesCompleted(object sender, GetCountryMatchesCompletedEventArgs e)
{
// Check for a web service error.
if (e.Error != null)
{
lblStatus.Text = e.Error.Message;
return;
}

lblStatus.Text = "Response received.";

// Set the suggestions.
autoCountry.ItemsSource = e.Result;

// Notify the control that the data has arrived.
autoCountry.PopulateComplete();
}

Step 16 : We are now ready to call WCF service to populate autoComplete textbox. So press F5 and type code in textbox to retrieve country name, say type 1 to get Australia; check yourself.



Try 2 to get America.



Conclusion:

SO here in this article we tried to call WCF service asynchronously for faster access to populate autocompletetextbox. We can extend this logic to other controls as well.

Hope you like this article.

Cheers.