Consume Web service from Silverlight

Calling web service from silverlight is as simple as in C#. In the following article I build a web service and call the web service from Microsoft silverlight. And I will discuss the the problem in the road to these sort of things.

First I build a Web service:

Add a ASP.NET Web Service application in your solution, and you will get an asmx file, write the services you want to expose in the service class. Here I write a simple service which shows child directory and files according to given parent directory.

All exposed service must have an attribute named [WebMethod].

As you want to call the web service from silverlight which is an scripting language you must add System.Web.Extension.dll into references and you must add the following attribute to your service class,

[System.Web.Script.Services.ScriptService]

So that you can call these services from any of the scripting language. These are the things all you have to do in web service project.

Now came to the silverlight application. Let we make a simple silverlight application which print the file and directory list in the canvas.

So you have to add web references to this web service. Mostly all there is an option find web services into this solution. And if your web service is not hosted in IIS then silverlight cannot use this web service. If the web service is hosted by runtime server then the port will be different other than 80, so silverlight handle it as different server and as it cannot handle cross domain call so you get an exception that you are trying to call cross domain services.

So, what you have to do is host your web services into IIS, and when you add web service reference you find web service from local host, and you will get the web service and hopefully you can call it without any exception. Adding web service reference will build a web service proxy in silverlight, you have to build an instance of these proxy and you can call these services in synchronous or asynchronous manner.

I write the following code in my default Page.xaml.cs in Page_load()

TextBlock block = new TextBlock();

block.SetValue<double>(Canvas.LeftProperty,5);

block.SetValue<double>(Canvas.TopProperty,5);

block.FontSize = 10;

block.Foreground = new SolidColorBrush(Colors.White);

localhost.WebServiceProxy proxy = new localhost.WebServiceProxy();

try

{

FileSystemData[] data = proxy.Contents(@"C:\Content");

// FileSystemData is my defined structure

for (int index = 0; index < data.Length; index++)

block.Text += data[index].FileName + "\r\n";

}

catch (Exception ex)

{

block.Text += ex.Message;

block.Text += ex.StackTrace;

}

this.Children.Add(block);

// all the codes are so simple that I don't write description about that.

the following code will print the content of directory C:\Content or it will print the exception. And finally the last trick you have to do is not run this project by F5 or run button, because it runs from file system, so that once again you will get cross domain exception. Just create a virtual directory in IIS for your silverlight project and run from localhost, hopefully all these will work fine.

Nothing is new in calling web service from silverlight just you have careful about cross domain and script permission that's it.