Multi tool use

Cannot access child value on JValue in Azure Mobile App

I recently implemented custom authentication with Azure Mobile App - All the server side works fine and also my web application which is using that mobile app service is working fine. I tested the server-side in details with POSTMAN and with different scenarios, everything works fine until I try to LoginAsync on Xamarin.

LoginAsync

When I pass email and password in POSTMAN, I get the following response as a clear indication that it is working

but when I send a request from my app using LoginAsync I get the following error.

LoginAsync

Cannot access child value on Newtonsoft.Json.Linq.JValue

My code to send request is fairly simple as following

public async Task<bool> Authenticate()
{
string username = "todo@gmail.com";
string password = "todo";
string message = string.Empty;
var success = false;
var credentials = new JObject
{
["email"] = username,
["password"] = password
};
try
{
MobileServiceUser user = await client.LoginAsync("CustomAuth", credentials);
if (user != null)
{
success = true;
CreateAndShowDialog("OK", "Auth");
}
}
catch (Exception ex)
{
CreateAndShowDialog(ex, "Auth Error");
}

return success;
}


where I am calling it as follows

private MobileServiceClient client;
client = new MobileServiceClient(applicationURL);
await Authenticate();


Any idea why I am getting Cannot access child value on Newtonsoft.Json.Linq.JValue error?

Cannot access child value on Newtonsoft.Json.Linq.JValue

Cheers

EDIT POST

As a workaround, I am temporarily using InvokeApiAsync with JObject.FromObject instead of LoginAsync

InvokeApiAsync

JObject.FromObject

LoginAsync

await client.InvokeApiAsync("/.auth/login/CustomAuth", JObject.FromObject(credentials), HttpMethod.Post, null);

await client.InvokeApiAsync("/.auth/login/CustomAuth", JObject.FromObject(credentials), HttpMethod.Post, null);

I am still not sure why LoginAsync does not work - Until I find a solution I will keep using InvokdeApiAsync as a workaround

LoginAsync

InvokdeApiAsync

var credentials = new JObject(new { email = username, password = password });

Could not determine JSON object type for type <>f__AnonymousType1

1 Answer
1

AFAIK, your initialization for credentials is correct. For the below error:

credentials

Cannot access child value on Newtonsoft.Json.Linq.JValue

I checked your testing result via POSTMAN and found that you did not return userId to your client. The essential properties returned to your client would look like as follows:

userId

{
"authenticationToken":"***",
"user":{
"userId":"***"
}
}


When using MobileServiceClient.LoginAsync, the client SDK would internally invoke LoginAsync() method under MobileServiceAuthentication.cs as follows:

MobileServiceClient.LoginAsync

LoginAsync()

JToken authToken = JToken.Parse(response);

// Get the Mobile Services auth token and user data
this.Client.CurrentUser = new MobileServiceUser((string)authToken["user"]["userId"]);

this.Client.CurrentUser.MobileServiceAuthenticationToken = (string)authToken[LoginAsyncAuthenticationTokenKey];


You would find that it would try to extract the userId property under user to construct the MobileServiceUser instance and assign to MobileServiceClient.CurrentUser.

userId

user

MobileServiceUser

MobileServiceClient.CurrentUser

InvokeApi

MobileServiceClient.CurrentUser

userId

authenticationToken

MobileServiceClient.LoginAsync

LoginAsync

MobileServiceClient.CurrentUser

reuse

authToken

MobileServiceClient

SharedPrefrences

null

lifetime

AppServiceLoginHandler.CreateToken

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.