RIA Services through Web Services

• RIA as Web Service demo

Introduction

I have been using Silverlight 4 and RIA Services on a large project lately and love how easy it is to expose a data layer with it. I was working on a different project with a co-worker using Silverlight 3 and my friend created proxies to get to the database and it was extremely messy code. I look back at it and just wondered what we were thinking about when we did it. Hind-sight is usually 20-20 and this was proving that saying since RIA Service is so much simpler to use.

I also create other things like iPhone/iPod/iPad apps using MonoTouch and am starting to look at the new MonoDroid for making android apps. One thing that would be very useful for a few of my projects will be a nice Web Service to save data into a SQL Server. I always could manually make a Web Service to get and store data off, but I wanted to see if there was any way to do it with RIA Services creating the data layer for me. It took some digging and searching but I found a way to do it and want to share this on the blog.

Machine Setup

To get this setup and running, I have Win7 running with the following software and toolkits. I did not have the RIA Services Toolkit at first and that was a problem that I will talk about later, but you should be able to run the code samples here using the following:

• Visual Studio 2010
• Silverlight 4
• RIA Services Toolkit
• Silverlight Developer Tools

Demo Project

I wanted to come up with a nice simple example. I am sick of NorthWind, and I cannot use the database I am using for my Silverlight projects that I am currently working on. So I came up with the idea of doing a task list system. I wanted this to be simple, so I setup the database using the following schema and filled the database with some sample data.

User Data

1	Steve
2	Joel
3	Paul
4	John

Task Data

1	1	Update Blog	1
2	1	Finish project	4
3	3	Buy coffee	1
4	4	Unpack from vacation	2
5	4	Report back to base	1

Silverlight / RIA Projects

I started this project with the Silverlight project that had RIA Services enabled in it. I added a new database to the sample web project and put the schema and data above into it. Then I added the Entity Framework Model to the web project as well and added both tables to it. After this, I added a Domain Service to the project to allow the Silverlight app to get to the data.

In the Silverlight project, I then added a combobox and a listbox to show the data. One of the things about using RIA Services is that calling the queries is done asynchronously. The Load method of the WebContext is used to call the query and provide a method to call with the results.

/// <summary>
/// Method to handle the loaded event to load up the users for the combobox
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    theContext.Load(theContext.GetUsersQuery(), OnUsersLoaded, null);
}
   
/// <summary>
/// Method called after the users are loaded from the RIA Service query
/// </summary>
/// <param name="loadOpp"></param>
void OnUsersLoaded(LoadOperation<Web.Models.User> loadOpp)
{
    comboBox1.Items.Clear();
    foreach (var item in loadOpp.AllEntities)
    {
        ComboBoxItem cbi = new ComboBoxItem();
        
        cbi.Content = (item as Web.Models.User).Name;
        cbi.Tag = item;
        comboBox1.Items.Add(cbi);
    }
}

Then on the selection change of the combobox, the tasks for the selected user needed to be loaded. Now since the query runs over the connection on the web server, I wanted to limit the data that was coming back. But by default, there was no method created to just get the tasks for a user, so I added the following method to the Domain Service.

/// <summary>
/// Method to get the tasks for a user
/// </summary>
/// <param name="userId">UserId for the user that we are getting the tasks for</param>
/// <returns></returns>
public IQueryable<Task> GetTasksByUser(int userId)
{
    return this.ObjectContext.Tasks.Where(t => t.UserId == userId);
}

Now I was able to query the RIA Service for just the tasks for the selected user. This code was then added to the Silverlight project to display the tasks.

/// <summary>
/// Method for handling the selection change on the user combobox 
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void comboBox1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    theContext.Load(theContext.GetTasksByUserQuery(((Web.Models.User)
	((ComboBoxItem)comboBox1.SelectedItem).Tag).UserId), OnTasksLoaded, null);
}
   
/// <summary>
/// Method to handle the return of the tasks from the RIA Service
/// </summary>
/// <param name="loadOpp"></param>
void OnTasksLoaded(LoadOperation<Web.Models.Task> loadOpp)
{
    listBox1.Items.Clear();
    foreach (var item in loadOpp.AllEntities)
    {
        listBox1.Items.Add((item as Web.Models.Task).Name);
    }
}

Now I had a Silverlight app that got its data from the web server and the database attached to it. It is a small simple sample of a Silverlight/RIA Services project that can be expanded on for more complicated projects.

Adding SOAP Endpoint

To allow a standard Web Service to be used, a SOAP endpoint needs to be added to the web.config. This was a simple thing to add to the web.config from samples that I found online. The highlighted section below was added to make sure that the wsdl is enabled for discovery.

<system.serviceModel>
    <domainServices>
      <endpoints>
        <add name="OData" 
	type="System.ServiceModel.DomainServices.Hosting.ODataEndpointFactory, 
	System.ServiceModel.DomainServices.Hosting.OData, Version=4.0.0.0, 
	Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
        <add name="Soap" 
	type="Microsoft.ServiceModel.DomainServices.Hosting.SoapXmlEndpointFactory, 
	Microsoft.ServiceModel.DomainServices.Hosting, Version=4.0.0.0, 
	Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
      </endpoints>
    </domainServices>
    <serviceHostingEnvironment aspNetCompatibilityEnabled="true" 
	multipleSiteBindingsEnabled="true" />
</system.serviceModel>     

Now I also need to add a reference to the Microsoft.ServiceModel.DomainServices.Hosting assembly. But I did not see this at all in the list of assemblies. I did some more searching and found that I needed to have the RIA Services Toolkit installed to have this available. I found this, installed it, and was up and ready to go.

Adding the reference and the app.config changes was what I thought I needed to do, but I had a small problem when I tried to reference the service. I could not get the name right. It turns out that the service automatically gets put into a virtual folder named ~\Services. All of the websites that have information on this say that the service is named by the namespace-class. One of the things that nobody says is that you need to change all '.' in the namespace or class into a '–'. Without using this type of naming, you will not be able to discover the service. When I ran my sample and tried to add the web service, I had to use the following address:

http://localhost:49423/Services/RIAasWebService-Web-Services-RiaWSDomainService.svc?wsdl

Client WPF App

I decided to use WPF as the client app since I use that the most and I can reuse some of the code from Silverlight to this project. I made the project the exact same as my Silverlight, with a single combobox and a listbox.

When I added the web service, I used an Advanced setting to add the async methods from the service. This allows you to call just like in the RIA Services call and get a callback when it is complete. I wanted to test out using it the other way, so I did not use these methods, but I checked them out to see if they were similar to the RIA Service versions and they are close. This simplified the functions to only two.

/// <summary>
/// Method for loading the users from the Web Service
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
    var users = ws.GetUsers();
   
    foreach (var item in users.RootResults)
    {
        ComboBoxItem cbi = new ComboBoxItem();
   
        cbi.Content = (item as User).Name;
        cbi.Tag = item;
        comboBox1.Items.Add(cbi);
    }
}
   
/// <summary>
/// Method for handling the selection change for the users to load the tasks
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void comboBox1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    var tasks = ws.GetTasksByUser(((User)
	((ComboBoxItem)comboBox1.SelectedItem).Tag).UserId);
    listBox1.Items.Clear();
    foreach (var item in tasks.RootResults)
    {
        listBox1.Items.Add((item as Task).Name);
    }
}

There is a bit of a delay in starting the app because it is calling the web service to get the users before it shows up, but this was expected with how I called the services.

Issues

There were a few issues as I was trying to get this up and running. The first, I already mentioned was the RIA Services Toolkit was needed to get things to work. Then there was the naming issue when I tried to connect to the service.

Using the ASP.NET Development Server, I could not connect to the service it was hosting from another machine. I would have to put the projects into IIS on my development machine and then expose it to the rest of my network. This would allow me to test it going to an iPhone app. I wish this was simpler, but the tasks to do this are not hard, however, I did not get this tested.

Conclusion

Having a RIA Service exposed so that it can be consumed like a standard Web Service can be a helpful thing. It allows non-Silverlight apps to use the same data and especially since Silverlight cannot run on an iPhone or Android based phone. To make some phone apps that all use the same information, this type of technique can be used. One thing to remember when you use this sample code is that you may have to refresh the web service with the localhost port that Visual Studio sets up for you. Or switch things to get it running in IIS. Good luck with it and I hope the code and article help.