I have tried mostly everything, I'm so frustrated at this stage, I would love if I can get an json object on the android side to use to populate a viewlist, I have tried formatting the json being sent in every way I possibly know how. Any suggestions would be amazing and very appreciated.
The JsonStringRequest recieves the json fine as a string, however to parse it to something useful has been a pain and I haven't managed to get a efficient way for the whole project. Trying to convert the string to either an JsonObject or Array fail with the same error.
The JsonArray- and Object-Request have both failed with similar error.
I have a feeling its not android side but the way I am sending the json from the rest service, or the way Volley is handling it.
Asp.net Web Api Controller class
using Newtonsoft.Json;
[RoutePrefix("users")]
public class UsersController : ApiController
{
public IHttpActionResult getUsers()
{
User[] users = new User[]
{
new User { userID = "one", Name = "Tomato Soup", Surname = "Groceries", Nickname = "boogie" },
new User { userID = "two", Name = "Tomato Soup", Surname = "Groceries", Nickname = "boogie" }
};
string json = JsonConvert.SerializeObject(users);
return Json(json);
}
}
The JSON for what is being sent:
"[{\"userID\":\"one\",\"Name\":\"Tomato Soup\",\"Surname\":\"Groceries\",\"Nickname\":\"boogie\"},{\"userID\":\"two\",\"Name\":\"Tomato Soup\",\"Surname\":\"Groceries\",\"Nickname\":\"boogie\"}]"
The XML for what is being sent:
[{"userID":"one","Name":"Tomato Soup","Surname":"Groceries","Nickname":"boogie"},{"userID":"two","Name":"Tomato Soup","Surname":"Groceries","Nickname":"boogie"}]
Android side request:
JsonObjectRequest (Very similar to JsonArrayRequest):
JsonObjectRequest request = new JsonObjectRequest("http://10.0.0.3/users",
new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response)
{
Log.w("##########", response.toString());
}
},
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.w("##########", error.getMessage());
}
}
) ;
queue.add(request);
StringRequest:
StringRequest req = new StringRequest("http://10.0.0.3/users", new Response.Listener<String>(){
public void onResponse(String response)
{
try
{
JSONObject jar = new JSONObject(response);
}
catch(JSONException error)
{
Log.w("error", error.getMessage());
}
Log.w("############", response);
Toast.makeText(getApplicationContext(), response, Toast.LENGTH_LONG);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error)
{
Log.w("error", error.getMessage());
Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG);
}
});
queue.add(req);
Logcat error:
org.json.JSONException: Value [{"userID":"one","Name":"Tomato Soup","Surname":"Groceries","Nickname":"boogie"},{"userID":"two","Name":"Tomato Soup","Surname":"Groceries","Nickname":"boogie"}] of type java.lang.String cannot be converted to JSONObject
Because the result is a JSONArray, you can use a JsonArrayRequest instead of JsonObjectRequest. If you have used JsonArrayRequest already and had any error, please post the error message or any logcat information with that JsonArrayRequest.
You can go here and here for more information
JSONObject: ...A string beginning with { (left brace) and ending with } (right brace).
JSONArray: ...A string that begins with [ (left bracket) and ends with ] (right bracket).
Hope this helps!
Wow, I figured it out. I was double serializing the user array object, it seems if I return the object without using the JsonConvert.SerializeObject it automatically serializes the object into a json. I'm not sure if its because its inherent to web api 2 (haven't read all the documentation yet). But thanks anyway.
Related
I have a question here about getting an Invalid Registration FCM error. I want to send notification to specific device through Backend .Net (EF)
First of all I saved the deviceToken to the server (Xamarin iOS).
I read the error from https://firebase.google.com/docs/cloud-messaging/http-server-ref
200 + error:InvalidRegistration Check the format of the registration
token you pass to the server. Make sure it matches the registration
token the client app receives from registering with Firebase
Notifications. Do not truncate or add additional characters.
public override void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)
{
//FirebasePushNotificationManager.DidRegisterRemoteNotifications(deviceToken);
//byte[] bytes = deviceToken.ToArray<byte>();
//string[] hexArray = bytes.Select(b => b.ToString("x2")).ToArray();
//DeviceToken = string.Join(string.Empty, hexArray);
string deviceTokenString;
if (UIDevice.CurrentDevice.CheckSystemVersion(13, 0))
{
deviceTokenString = BitConverter.ToString(deviceToken.ToArray());
}
else
{
deviceTokenString = deviceToken.ToString();
}
Preferences.Set("TokenDevice", deviceTokenString);
}
I saved the deviceToken to Preferences and also saved it to the server. My deviceToken code on Xamarin iOS:
1A-F5-BE-DC-E4-22-07-46-AA-C4-87-CC-08-F5-D7-09-D4-AB-43-18-26-E0-65-3B-39-4E-6F-5E-02-35-9E-3A
I don't know if this method of getting the deviceToken on Xamarin iOS is really correct at this time?
Backend I write API to send:
private static Uri FireBasePushNotificationsURL = new Uri("https://fcm.googleapis.com/fcm/send");
private static string ServerKey = "key=AAAAqOId6Is:APxxxxxxxxxxxxxxxxxxxx....";
[HttpPost]
public async void PushNotificationToFCM(string deviceTokens, string title, string body, object data, string linkdirection)
{
using (var client = new HttpClient())
{
var messageInformation = new Message()
{
notification = new NotificationFirebases()
{
title = title,
text = body
},
data = new Dictionary<string, string>()
{
{ "link", linkdirection },
},
to = deviceTokens
};
//Object to JSON STRUCTURE => using Newtonsoft.Json;
string jsonMessage = JsonConvert.SerializeObject(messageInformation);
string postBody = JsonConvert.SerializeObject(messageInformation).ToString();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.TryAddWithoutValidation("Authorization", ServerKey);
var response = client.PostAsync(FireBasePushNotificationsURL, new StringContent(postBody, Encoding.UTF8, "application/json"));
var responseString = response.Result.Content.ReadAsStringAsync().Result;
}
}
public class Message
{
public string to { get; set; }
public NotificationFirebases notification { get; set; }
public object data { get; set; }
}
public class NotificationFirebases
{
public string title { get; set; }
public string text { get; set; }
}
When I test I get the error:
{\"multicast_id\":7343900550378569449,\"success\":0,\"failure\":1,\"canonical_ids\":0, \" results\":[{\"error\":\"InvalidRegistration\"}]}. I have tried with deviceToken on Android and it succeeds. Appears only with deviceToken on Xamarin iOS
Please note that I tried sending a notification in Firebase Cloud Messaging: https://console.firebase.google.com/u/0/project/.... then I got a notification, so you can see that my APNS configuration is not wrong.
Looking forward to everyone's help. I also spent more than 2 weeks searching and trying to no avail. Thank you very much.
Update Backend I write API to send:
public void PushNotificationToFCM(string deviceTokens, string title, string body, object data, string linkdirection)
{
FirebaseApp.Create(new AppOptions() {
Credential= GoogleCredential.FromFile("private_key.json")
});
// This registration token comes from the client FCM SDKs.
var registrationToken = deviceTokens;
// See documentation on defining a message payload.
var message = new Message()
{
Apns = new ApnsConfig { Aps = new Aps { ContentAvailable = true, Sound = "default" } },
Data = new Dictionary<string, string>()
{
{ "link", linkdirection },
},
Token = registrationToken,
Notification= new FirebaseAdmin.Messaging.Notification()
{
Title = title,
Body = body,
}
};
// Send a message to the device corresponding to the provided
// registration token.
string response = FirebaseMessaging.DefaultInstance.SendAsync(message).Result;
// Response is a message ID string.
Debug.WriteLine("Successfully sent message: " + response);
}
I don't know if such iOS device's TokenDevice code is correct? I tried to submit it, however getting the error: System.AggregateException: 'One or more errors occurred. (The registration token is not a valid FCM registration token)'
I uninstalled and reinstalled the app, I got a new tokenDevice. However when I send the notification I still get the same error
As an alternative workaround, you can use this NuGet package Plugin.FirebasePushNotification.
1. After Creating the iOS Project, add "GoogleService-Info.plist" file to your iOS Project and update the property to BundleResource.
2. In Info.plist and FinishedLaunching method, add following line:
<key>FirebaseAppDelegateProxyEnabled</key>
<false/>
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
global::Xamarin.Forms.Forms.Init();
LoadApplication(new App());
FirebasePushNotificationManager.Initialize(options, true);
return base.FinishedLaunching(app, options);
}
3. Then add the below in App Construct.
CrossFirebasePushNotification.Current.OnTokenRefresh += (s, p) =>
{
System.Diagnostics.Debug.WriteLine($"TOKEN : {p.Token}");
};
CrossFirebasePushNotification.Current.OnNotificationReceived += (s, p) =>
{
System.Diagnostics.Debug.WriteLine("Received");
foreach (var data in p.Data)
{
System.Diagnostics.Debug.WriteLine($"{data.Key} : {data.Value}");
}
};
CrossFirebasePushNotification.Current.OnNotificationOpened += (s, p) =>
{
System.Diagnostics.Debug.WriteLine("Opened");
foreach (var data in p.Data)
{
System.Diagnostics.Debug.WriteLine($"{data.Key} : {data.Value}");
}
};
4. After getting the FCM registration token. then click Test, the targeted client device (with the app in the background) should receive the notification in the system notifications tray.
I am learning Blazor, and I have a WebAssembly client application.
I created a WebAPI at the server which does some additional validation over and above the standard data annotation validations. For example, as it attempts to write a record to the database it checks that no other record exists with the same email address. Certain types of validation can't reliably happen at the client, particularly where race conditions could produce a bad result.
The API controller returns a ValidationProblem result to the client, and Postman shows the body of the result as:
{
"type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
"title": "One or more validation errors occurred.",
"status": 400,
"traceId": "|f06d4ffe-4aa836b5b3f4c9ae.",
"errors": {
"Email": [
"The email address already exists."
]
}
}
Note that the validation error is in the "errors" array in the JSON.
Back in the Blazor Client application, I have the typical HandleValidSubmit function that posts the data to the API and receives a response, as shown here:
private async void HandleValidSubmit()
{
var response = await Http.PostAsJsonAsync<TestModel>("api/Test", testModel);
if (response.StatusCode != System.Net.HttpStatusCode.Created)
{
// How to handle server-side validation errors?
}
}
My question is, how to best process server-side validation errors? The user experience ought to be the same as any other validation error, with the field highlighted, the validation message shown, and the summary at the top of the page.
I ended up solving this by creating a ServerValidator component. I'll post the code here in case it is helpful for others seeking a solution to the same problem.
This code assumes you are calling a Web API endpoint that returns a ValidationProblem result if there are issues.
public class ServerValidator : ComponentBase
{
[CascadingParameter]
EditContext CurrentEditContext { get; set; }
protected override void OnInitialized()
{
base.OnInitialized();
if (this.CurrentEditContext == null)
{
throw new InvalidOperationException($"{nameof(ServerValidator)} requires a cascading " +
$"parameter of type {nameof(EditContext)}. For example, you can use {nameof(ServerValidator)} " +
$"inside an EditForm.");
}
}
public async void Validate(HttpResponseMessage response, object model)
{
var messages = new ValidationMessageStore(this.CurrentEditContext);
if (response.StatusCode == HttpStatusCode.BadRequest)
{
var body = await response.Content.ReadAsStringAsync();
var validationProblemDetails = JsonSerializer.Deserialize<ValidationProblemDetails>(body);
if (validationProblemDetails.Errors != null)
{
messages.Clear();
foreach (var error in validationProblemDetails.Errors)
{
var fieldIdentifier = new FieldIdentifier(model, error.Key);
messages.Add(fieldIdentifier, error.Value);
}
}
}
CurrentEditContext.NotifyValidationStateChanged();
}
// This is to hold the response details when the controller returns a ValidationProblem result.
private class ValidationProblemDetails
{
[JsonPropertyName("status")]
public int? Status { get; set; }
[JsonPropertyName("title")]
public string Title { get; set; }
[JsonPropertyName("type")]
public string Type { get; set; }
[JsonPropertyName("errors")]
public IDictionary<string, string[]> Errors { get; set; }
}
}
To use this new component, you will need to add the component within your EditForm:
<EditForm Model="agency" OnValidSubmit="HandleValidSubmit">
<ServerValidator #ref="serverValidator" />
<ValidationSummary />
... put all your form fields here ...
</EditForm>
Lastly, you can kick off the validation in your #code section:
#code {
private TestModel testModel = new TestModel();
private ServerValidator serverValidator;
private async void HandleValidSubmit()
{
var response = await Http.PostAsJsonAsync<TestModel>("api/TestModels", testModel);
if (response.StatusCode != System.Net.HttpStatusCode.Created)
{
serverValidator.Validate(response, testModel);
}
else
{
Navigation.NavigateTo(response.Headers.Location.ToString());
}
}
}
In theory, this ought to allow you to bypass client validation entirely and rely on your Web API to do it. In practice, I found that Blazor performs client validation when there are annotations on your model, even if you don't include a <DataAnnotationsValidator /> in your form. However, it will still catch any validation issues at the server and return them to you.
how to best process server-side validation errors? The user experience ought to be the same as any other validation error, with the field highlighted, the validation message shown, and the summary at the top of the page.
I don't know what comes in your response, so I made a generic version of a component that do what you need.
Get the CascadingParameter of the EditContext
[CascadingParameter]
public EditContext EditContext { get; set; }
Have a ValidationMessageStore to hold the errors and a function that will display the errors
private ValidationMessageStore _messageStore;
private EventHandler<ValidationRequestedEventArgs> OnValidationRequested => (s, e) =>
{
_messageStore.Clear();
};
private EventHandler<FieldChangedEventArgs> OnFieldChanged => (s, e) =>
{
_messageStore.Clear(e.FieldIdentifier);
};
protected override void OnInitialized()
{
base.OnInitialized();
if (EditContext != null)
{
_messageStore = new ValidationMessageStore(EditContext);
EditContext.OnFieldChanged += OnFieldChanged;
EditContext.OnValidationRequested += OnValidationRequested;
}
}
public override void Dispose()
{
base.Dispose();
if (EditContext != null)
{
EditContext.OnFieldChanged -= OnFieldChanged;
EditContext.OnValidationRequested -= OnValidationRequested;
}
}
private void AddFieldError(ERROR_CLASS_YOU_ARE_USING validatorError)
{
_messageStore.Add(EditContext.Field(validatorError.FIELD_NAME), validatorError.ERROR_MESSAGE);
}
Call the function of the component using it's ref
private async void HandleValidSubmit()
{
var response = await Http.PostAsJsonAsync<TestModel>("api/Test", testModel);
if (response.StatusCode != System.Net.HttpStatusCode.Created)
{
// How to handle server-side validation errors?
// You could also have a foreach or a function that receives an List for multiple fields error display
MyHandleErrorComponent.AddFieldError(response.ERROR_PROPERTY);
}
}
https://learn.microsoft.com/en-us/aspnet/core/blazor/forms-validation has an example of how to handle server-side validation errors:
private async Task HandleValidSubmit(EditContext editContext)
{
customValidator.ClearErrors();
try
{
var response = await Http.PostAsJsonAsync<Starship>(
"StarshipValidation", (Starship)editContext.Model);
var errors = await response.Content
.ReadFromJsonAsync<Dictionary<string, List<string>>>();
if (response.StatusCode == HttpStatusCode.BadRequest &&
errors.Count() > 0)
{
customValidator.DisplayErrors(errors);
}
else if (!response.IsSuccessStatusCode)
{
throw new HttpRequestException(
$"Validation failed. Status Code: {response.StatusCode}");
}
else
{
disabled = true;
messageStyles = "color:green";
message = "The form has been processed.";
}
}
catch (AccessTokenNotAvailableException ex)
{
ex.Redirect();
}
catch (Exception ex)
{
Logger.LogError("Form processing error: {Message}", ex.Message);
disabled = true;
messageStyles = "color:red";
message = "There was an error processing the form.";
}
}
Use two phase validation.
Hook up an event for when the email is entered which calls an "IsEmailUnique" method on your api. This offers your user real time validation information. Perhaps disable the "Save" button until the email has been validated on the server.
You can then handle the Bad Request as you would any other server-side errors.
I want to know exactly why this is not working:
[HttpPost]
public IHttpActionResult Post(Slack_Webhook json)
{
return Ok(json.challenge);
}
public class Slack_Webhook
{
public string type { get; set; }
public string token { get; set; }
public string challenge { get; set; }
}
The Official Documentation says:
We’ll send HTTP POST requests to this URL when events occur. As soon
as you enter a URL, we’ll send a request with a challenge parameter,
and your endpoint must respond with the challenge value.
This is an example object (JSON) sent by Slack:
{
"token": "Jhj5dZrVaK7ZwHHjRyZWjbDl",
"challenge": "3eZbrw1aBm2rZgRNFdxV2595E9CY3gmdALWMmHkvFXO7tYXAYM8P",
"type": "url_verification"
}
EDIT:
I could write a book on code that does not work in this issue... here's another example that did not work - still no idea what is wrong:
[HttpPost]
public IHttpActionResult Post()
{
var pairs = Request.GetQueryNameValuePairs();
bool isValidToken = false;
string c = "This does not work.";
foreach(var pair in pairs)
{
if (pair.Key == "token")
{
if (pair.Value == "<UNIQUETOKEN>")
{
isValidToken = true;
}
}
if (pair.Key == "challenge")
{
c = pair.Value;
}
}
if (isValidToken == true)
{
return Json(new {challenge = c });
}
else
{
return BadRequest();
}
}
EDIT2:
Very interesting that I get NULL as a response from below code - that means the body of the received POST is empty.. Could anyone with a working Slack-Integration try that out? So their site is wrong, stating the challenge is sent in the body - where else could it be?
// POST: api/Slack
[HttpPost]
public IHttpActionResult Post([FromBody]string json)
{
return Json(json);
}
EDIT3:
This function is used to get the raw request, but there is nothing inside the body - I am out of solutions.. the support of Slack said, they have no idea about ASP.NET and I should ask here on SO for a solution. Here we are again! ;-)
[HttpPost]
public async Task<IHttpActionResult> ReceivePostAsync()
{
string rawpostdata = await RawContentReader.Read(this.Request);
return Json(new StringContent( rawpostdata));
}
public class RawContentReader
{
public static async Task<string> Read(HttpRequestMessage req)
{
using (var contentStream = await req.Content.ReadAsStreamAsync())
{
contentStream.Seek(0, SeekOrigin.Begin);
using (var sr = new StreamReader(contentStream))
{
return sr.ReadToEnd();
}
}
}
}
The result ( as expected ) looks like this:
Our Request:
POST
"body": {
"type": "url_verification",
"token": "<token>",
"challenge": "<challenge>"
}
Your Response:
"code": 200
"error": "challenge_failed"
"body": {
{"Headers":[{"Key":"Content-Type","Value":["text/plain; charset=utf-8"]}]}
}
I think I'm missing something - is there another way to get the body of the POST-Request? I mean, I can get everything else - except the body ( or it says it is empty).
EDIT4:
I tried to read the body with another function I found - without success, returns empty string - but to let you know what I already tried, here it is:
[HttpPost]
public IHttpActionResult ReceivePost()
{
var bodyStream = new
StreamReader(HttpContext.Current.Request.InputStream);
bodyStream.BaseStream.Seek(0, SeekOrigin.Begin);
var bodyText = bodyStream.ReadToEnd();
return Json(bodyText);
}
While trying to solve this I learnt a lot - but this one seems to be so impossible, that I think I will never solve it alone. Thousands of tries with thousands of different functions - I have tried hundreds of parameters and functions in all of WebApi / ASP.NET / MVC / whatever - why is there no BODY? Does it exist? What's his/her name? Where does it live? I really wanna hang out with that parameter if I ever find it, must be hidden at the end of the rainbow under a pot of gold.
If you can use ASP.NET Core 2, this will do the trick:
public async Task<ActionResult> HandleEvent([FromBody] dynamic data)
=> new ContentResult {Content = data.challenge};
According to the official documentation linked to in the OP you have to format your response depending on the content type you return.
It is possible you are not returning the value (challenge) in one of the expected formats.
Once you receive the event, respond in plaintext with the challenge
attribute value. In this example, that might be:
HTTP 200 OK
Content-type: text/plain
3eZbrw1aBm2rZgRNFdxV2595E9CY3gmdALWMmHkvFXO7tYXAYM8P
To do the above you would have needed to return your request differently
[HttpPost]
public IHttpActionResult Post([FromBody]Slack_Webhook json) {
//Please verify that the token value found in the payload
//matches your application's configured Slack token.
if (ModelState.IsValid && json != null && ValidToken(json.token)) {
var response = Request.CreateResponse(HttpStatusCode.OK, json.challenge, "text/plain");
return ResponseMessage(response);
}
return BadRequest();
}
Documentation also shows
Or even JSON:
HTTP 200 OK
Content-type: application/json
{"challenge":"3eZbrw1aBm2rZgRNFdxV2595E9CY3gmdALWMmHkvFXO7tYXAYM8P"}
Which again would have to be formatted a little differently
[HttpPost]
public IHttpActionResult Post([FromBody]Slack_Webhook json) {
//Please verify that the token value found in the payload
//matches your application's configured Slack token.
if (ModelState.IsValid && json != null && ValidToken(json.token)) {
var model = new { challenge = json.challenge };
return Ok(model);
}
return BadRequest();
}
Here's how you can access the data:
[HttpPost]
[Route("something")]
public JsonResult DoSomething()
{
var token = HttpContext.Request.Form["token"];
// Is the same as:
// var token = Request.Form["token"];
return new JsonResult(token);
}
I suggest using a Request Bin for further debugging.
I'm writing a Nancy endpoint and I want to do something that I think should be really simple. I want to support returning the content in either json or xml but when html or any other type is requested to return a 406 Not supported. I can easily force either XML or JSON only, and I guess I could do and if (accept is html) return 406 but I would assume that there is some support for this in the content Negotiation support.
Can anybody shed any light?
Implement your own IResponseProcessor, Nancy will pick it up and hook in the engine.
public sealed class NoJsonOrXmlProcessor : IResponseProcessor
{
public ProcessorMatch CanProcess(MediaRange requestedMediaRange, dynamic model, NancyContext context)
{
if (requestedMediaRange.Matches("application/json") || requestedMediaRange.Matches("aaplication/xml"))
{
//pass on, so the real processors can handle
return new ProcessorMatch{ModelResult = MatchResult.NoMatch, RequestedContentTypeResult = MatchResult.NoMatch};
}
return new ProcessorMatch{ModelResult = MatchResult.ExactMatch, RequestedContentTypeResult = MatchResult.ExactMatch};
}
public Response Process(MediaRange requestedMediaRange, dynamic model, NancyContext context)
{
return new Response{StatusCode = HttpStatusCode.NotAcceptable};
}
public IEnumerable<Tuple<string, MediaRange>> ExtensionMappings { get; private set; }
}
We avoided the use of ResponseProcessor for the whole reason that the request was still being run all the way through our authentication layer, domain layer, etc. We wanted a way to quickly kill the request as soon as possible.
What we ended up doing was performing the check inside our own Boostrapper
public class Boostrapper : DefaultNancyBootstrapper
{
protected override void RequestStartup(TinyIoCContainer requestContainer, IPipelines pipelines, NancyContext context)
{
base.RequestStartup(requestContainer, pipelines, context);
pipelines.BeforeRequest += nancyContext =>
{
RequestHeaders headers = nancyContext.Request.Headers
if (!IsAcceptHeadersAllowed(headers.Accept))
{
return new Response() {StatusCode = HttpStatusCode.NotAcceptable};
}
return null;
}
}
private bool IsAcceptHeadersAllowed(IEnumerable<Tuple<string, decimal>> acceptTypes)
{
return acceptTypes.Any(tuple =>
{
var accept = new MediaRange(tuple.Item1);
return accept.Matches("application/json") || accept.Matches("application/xml");
});
}
}
I have been experimenting with WP7 apps today and have hit a bit of a wall.
I like to have seperation between the UI and the main app code but Ive hit a wall.
I have succesfully implemented a webclient request and gotten a result, but because the call is async I dont know how to pass this backup to the UI level. I cannot seem to hack in a wait for response to complete or anything.
I must be doing something wrong.
(this is the xbox360Voice library that I have for download on my website: http://www.jamesstuddart.co.uk/Projects/ASP.Net/Xbox_Feeds/ which I am porting to WP7 as a test)
here is the backend code snippet:
internal const string BaseUrlFormat = "http://www.360voice.com/api/gamertag-profile.asp?tag={0}";
internal static string ResponseXml { get; set; }
internal static WebClient Client = new WebClient();
public static XboxGamer? GetGamer(string gamerTag)
{
var url = string.Format(BaseUrlFormat, gamerTag);
var response = GetResponse(url, null, null);
return SerializeResponse(response);
}
internal static XboxGamer? SerializeResponse(string response)
{
if (string.IsNullOrEmpty(response))
{
return null;
}
var tempGamer = new XboxGamer();
var gamer = (XboxGamer)SerializationMethods.Deserialize(tempGamer, response);
return gamer;
}
internal static string GetResponse(string url, string userName, string password)
{
if (!string.IsNullOrEmpty(userName) && !string.IsNullOrEmpty(password))
{
Client.Credentials = new NetworkCredential(userName, password);
}
try
{
Client.DownloadStringCompleted += ClientDownloadStringCompleted;
Client.DownloadStringAsync(new Uri(url));
return ResponseXml;
}
catch (Exception ex)
{
return null;
}
}
internal static void ClientDownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
if (e.Error == null)
{
ResponseXml = e.Result;
}
}
and this is the front end code:
public void GetGamerDetails()
{
var xboxManager = XboxFactory.GetXboxManager("DarkV1p3r");
var xboxGamer = xboxManager.GetGamer();
if (xboxGamer.HasValue)
{
var profile = xboxGamer.Value.Profile[0];
imgAvatar.Source = new BitmapImage(new Uri(profile.ProfilePictureMiniUrl));
txtUserName.Text = profile.GamerTag;
txtGamerScore.Text = int.Parse(profile.GamerScore).ToString("G 0,000");
txtZone.Text = profile.PlayerZone;
}
else
{
txtUserName.Text = "Failed to load data";
}
}
Now I understand I need to place something in ClientDownloadStringCompleted but I am unsure what.
The problem you have is that as soon as an asynchronous operation is introduced in to the code path the entire code path needs to become asynchronous.
Because GetResponse calls DownloadStringAsync it must become asynchronous, it can't return a string, it can only do that on a callback
Because GetGamer calls GetResponse which is now asynchronous it can't return a XboxGamer, it can only do that on a callback
Because GetGamerDetails calls GetGamer which is now asynchronous it can't continue with its code following the call, it can only do that after it has received a call back from GetGamer.
Because GetGamerDetails is now asynchronous anything call it must also acknowledge this behaviour.
.... this continues all the way up to the top of the chain where a user event will have occured.
Here is some air code that knocks some asynchronicity in to the code.
public static void GetGamer(string gamerTag, Action<XboxGamer?> completed)
{
var url = string.Format(BaseUrlFormat, gamerTag);
var response = GetResponse(url, null, null, (response) =>
{
completed(SerializeResponse(response));
});
}
internal static string GetResponse(string url, string userName, string password, Action<string> completed)
{
WebClient client = new WebClient();
if (!string.IsNullOrEmpty(userName) && !string.IsNullOrEmpty(password))
{
client.Credentials = new NetworkCredential(userName, password);
}
try
{
client.DownloadStringCompleted += (s, args) =>
{
// Messy error handling needed here, out of scope
completed(args.Result);
};
client.DownloadStringAsync(new Uri(url));
}
catch
{
completed(null);
}
}
public void GetGamerDetails()
{
var xboxManager = XboxFactory.GetXboxManager("DarkV1p3r");
xboxManager.GetGamer( (xboxGamer) =>
{
// Need to move to the main UI thread.
Dispatcher.BeginInvoke(new Action<XboxGamer?>(DisplayGamerDetails), xboxGamer);
});
}
void DisplayGamerDetails(XboxGamer? xboxGamer)
{
if (xboxGamer.HasValue)
{
var profile = xboxGamer.Value.Profile[0];
imgAvatar.Source = new BitmapImage(new Uri(profile.ProfilePictureMiniUrl));
txtUserName.Text = profile.GamerTag;
txtGamerScore.Text = int.Parse(profile.GamerScore).ToString("G 0,000");
txtZone.Text = profile.PlayerZone;
}
else
{
txtUserName.Text = "Failed to load data";
}
}
As you can see async programming can get realy messy.
You generally have 2 options. Either you expose your backend code as an async API as well, or you need to wait for the call to complete in GetResponse.
Doing it the async way would mean starting the process one place, then return, and have the UI update when data is available. This is generally the preferred way, since calling a blocking method on the UI thread will make your app seem unresponsive as long as the method is running.
I think the "Silverlight Way" would be to use databinding. Your XboxGamer object should implement the INotifyPropertyChanged interface. When you call GetGamer() it returns immediately with an "empty" XboxGamer object (maybe with GamerTag=="Loading..." or something). In your ClientDownloadStringCompleted handler you should deserialize the returned XML and then fire the INotifyPropertyChanged.PropertyChanged event.
If you look at the "Windows Phone Databound Application" project template in the SDK, the ItemViewModel class is implemented this way.
Here is how you can expose asynchronous features to any type on WP7.