Detecting when a web service post has occured - windows-phone-8

Question

I just wrote a simple windows 8 form that post to web service api. It works fine. But my challenge is been able to determine when the post operation was a success and a failure. I dont know how to return a value cos aysnc Task is not allowing a return type.
//This class does the post to web service
public class B2cMobileuserService : IB2cMobileuserService
{
private string RegisterUserUrl = RestfulUrl.RegisterMobileUser;
private readonly HttpClient _client = new HttpClient();
public async Task RegisterMobileUser(B2cMobileuserView user)
{
var jsonString = Serialize(user);
var content = new StringContent(jsonString, Encoding.UTF8, "application/json");
var result = await _client.PostAsync(RegisterUserUrl, content);
}
}
//This class calls the one above
public class WebserviceProcessor
{
//declaring all the service objects that would be used
IB2cMobileuserService mobileuserService = null;
public WebserviceProcessor() {
mobileuserService = new B2cMobileuserService();
}
//This method is going to post values to the web serever
public async void RegisterUser(B2cMobileuserView mobileuser) {
mobileuserService.RegisterMobileUser(mobileuser);
}
}
//Then the code below is from my .xaml user interface that calls the class that sends to webservice
private void Button_Click(object sender, RoutedEventArgs e)
{
B2cMobileuserView user = new B2cMobileuserView();
user.Name = name.Text;
user.Email = email.Text;
user.PhoneType = "Windows Mobile";
user.BrowserType = "None";
user.CountryName = "Nigeria";
user.UserPhoneID = phone.Text;
Serviceprocessor.RegisterUser(user);
progressBar.Visibility = Visibility.Visible;
}
Please I dont know how to return a value cos when I try I get the error that says async method must be void.
I need to set a way to know when the post was a success based on the return value from the web service.

Answer 1

To ensure the POST was successful, call HttpResponseMessage.EnsureSuccessStatusCode:
public async Task RegisterMobileUser(B2cMobileuserView user)
{
var jsonString = Serialize(user);
var content = new StringContent(jsonString, Encoding.UTF8, "application/json");
var result = await _client.PostAsync(RegisterUserUrl, content);
result.EnsureSuccessStatusCode();
}
If you want to return a value, use a Task<T> return type instead of Task.
On a side note, avoid async void; use async Task instead of async void unless the compiler forces you to write async void:
//This method is going to post values to the web serever
public Task RegisterUser(B2cMobileuserView mobileuser) {
return mobileuserService.RegisterMobileUser(mobileuser);
}
Also, you should name your asynchronous methods ending in *Async:
//This method is going to post values to the web serever
public Task RegisterUserAsync(B2cMobileuserView mobileuser) {
return mobileuserService.RegisterMobileUserAsync(mobileuser);
}
You may find my async intro and MSDN article on async best practices helpful.