Using ASP.NET Authentication in a Web Service with Silverlight

A reader recently asked me to expand on the ASP.NET Authentication + Silverlight concept I started.. Specifically they wanted to do know how they can have a web service that returns different results depending on who calls the service (and what role they are in). 

Here is my quick walk through of adding that capability to the Silverlight+ASP.NET AppServices sample.

First, let's look at the scenario we are trying to enable.  I wanted to add a "Fire Bob" button. Hopefully, no line of business application has a "fire employee" button, but I thought it showed of the concepts well.   Clearly only managers should be able to fire bob, so the button should be grayed out if you are not logged in or logged in but not in the manager role. 

Logging as manager enables the button and clicking on it actually does the firing and reports status.  Notice the background color is a user preference of manager. 

And when logged in as an employee, the button is grayed out.

Defining the service

The first step to enabling this is to define a web service that will fire the employee and offer a way to check to see if you can fire the employee. 

In the web project, add a new item and select the new (in Beta2) Silverlight-enabled WCF service

Then define the service as such:

using System;
using System.ServiceModel;
using System.ServiceModel.Activation;
using System.Web;

[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = 
AspNetCompatibilityRequirementsMode.Allowed)]
public class FireEmployeeService2
{
    [OperationContract]
    public void FireEmployee(string employeeName)
    {
        if (CanFireEmployees())
        {
            DoTheDirtyWork(employeeName);
        }

    }
    public void DoTheDirtyWork(string employeeName)
    {
        //Proceed to fire the employee

    }
    [OperationContract]
    public bool CanFireEmployees()
    {
        return HttpContext.Current.User.IsInRole("Management");

    }
}

Notice we are defining two entry points, one to check (CanFireEmployees) and one the actually fire. Clearly in a real world scenario you'd want a few more checks here and more of a model where you start a workflow..    The key thing here is the call to User.IsInRole().. the great thing here is that logging in on the client means you are also logged in on the server!  So this just works. 

In the Silverlight project, right click and add a service reference.  Hit "Discover" and select the right one.

In the login_Competed method, go ahead and check to see if this person can fire the employee

FireEmployeeService2Client fireClient = new FireEmployeeService2Client();
fireClient.CanFireEmployeesAsync();
fireClient.CanFireEmployeesCompleted += 
    new EventHandler<CanFireEmployeesCompletedEventArgs>(fireClient_CanFireEmployeesCompleted);
this.fireButton.IsEnabled = false;

Then when the call completes,simply set the buttons enable status based on the results. 

void fireClient_CanFireEmployeesCompleted(object sender, CanFireEmployeesCompletedEventArgs e)
 {
     this.fireButton.IsEnabled = e.Result;
 }

Then, the actual implementation of the fire button is streight forward, following all the patterns we have setup for this sort of thing. 

private void fireButton_Click(object sender, RoutedEventArgs e)
 {
     this.fireLabel.Text = "Trying to fire...";
     var client = new FireEmployeeService2Client();
     client.FireEmployeeAsync("bob");
     client.FireEmployeeCompleted += new EventHandler<AsyncCompletedEventArgs>(client_FireEmployeeCompleted);
 }

 void client_FireEmployeeCompleted(object sender, AsyncCompletedEventArgs e)
 {

     if (e.Error != null)
         fireLabel.Text = e.Error.ToString();
     else
         fireLabel.Text = "Call Succeed";
 }

Hope that helps!  you can get the full project here.