I use RestSharp to pass data between the clien-side (Xamarin android app) and my server.
When there is an error (usually because the server is down) the method that execute the request throw an exception.
I want the exception to go back all the way to the method who called it, so I can throw an error to the user.
For example, I want to login, but lets say the server is down.
A - The method that execute the request
public Task<T> ExecuteAsync<T>(RestRequest request) where T : new()
{
var client = new RestClient
{
BaseUrl = new Uri(BaseUrl),
Authenticator = new HttpBasicAuthenticator(_accountName, _password)
};
var taskCompletionSource = new TaskCompletionSource<T>();
client.ExecuteAsync<T>(request, restResponse =>
{
if (restResponse.ErrorException != null)
{
throw (new Exception("Server returned an error"));
}
taskCompletionSource.SetResult(restResponse.Data);
});
return taskCompletionSource.Task;
}
B - Method that uses method A to execute a request
public static async Task<LoginObject> Login(string accessNumber, string password, string token)
{
var request = new RestRequest
{
Method = Method.POST,
Resource = "Login"
};
request.AddJsonBody(
new
{
accessNumber = accessNumber,
password = password,
token = token
});
var isDone = await Api.ExecuteAsync<LoginObject>(request);
return isDone;
}
C - The method where I want to handle the exception
public async Task Login(string PhoneNumber, string Password)
{
try
{
LoginObject login = await LoginServices.Login(PhoneNumber, Password, Token);
if (login.IsOk)
{
// Move to next activity
}
else
{
Toast.MakeText(this, "Login Error", ToastLength.Short).Show();
}
}
catch (Exception ex) // Here I want to throw the server error
{
Toast.MakeText(this, "Server Error", ToastLength.Short).Show();
return null;
}
}
Now when I run the code, the error is being thrown in A, and the app crash,
I want it to go from A to B and from B to C, and then I'll show an error to the user.
Edit: I tried to put a try/catch block but it still throws the exception in A.
Change method A to have async in the signature and then change your last line to return await taskCompletionSource.Task;
In your A-method, please use taskCompletionSource.SetException like this:
if (restResponse.ErrorException != null)
{
//throw new Exception("Server returned an error");
taskCompletionSource.SetException(new Exception("Server returned an error"));
}
else
{
taskCompletionSource.SetResult(restResponse.Data);
}
In your B-method replace this line:
var isDone = await Api.ExecuteAsync<LoginObject>(request);
with this to re-throw the exception to you C-method:
LoginObject isDone=null;
try
{
isDone = await Api.ExecuteAsync<LoginObject>(request);
}
catch (Exception e)
{
throw e;
}
This article is talking about TaskCompletionSource
Related
I have used the aws-samples example named aws-cognito-dot-net-desktop-app in C# and Android:
aws-cognito-dot-net-desktop-app
It works very well and correctly registers the user in Cognito.
To register a user, do the following:
bool success = await helper.SignUpUser(etUserName.Text, etPasswordUser.Text, etEmailUser.Text, etPhoneUser.Text);
That way the user is created, but a code needs to be entered that is sent to the user's email. The code entry is as follows:
CognitoHelper cognitoHelper = new CognitoHelper();
return await cognitoHelper.VerifyAccessCode(userName, codeSentToMail);
and the user registers without problems, that is to say, it works correctly:
Now I want to delete any user created, for which I am creating a task as follows:
internal async Task<bool> DeleteUser(string username)
{
try
{
AmazonCognitoIdentityProviderClient provider =
new Amazon.CognitoIdentityProvider.AmazonCognitoIdentityProviderClient(new Amazon.Runtime.AnonymousAWSCredentials(), RegionEndpoint.USEast1);
DeleteUserPoolRequest request = new DeleteUserPoolRequest();
request.UserPoolId = username;
DeleteUserPoolResponse deleteUserPoolClientResponse = await provider.DeleteUserPoolAsync(request);
return true;
}
catch (Exception ex)
{
Console.WriteLine(ex);
return false;
}
}
When executing DeleteUserPoolRequest, an exception is thrown indicating an error of type Amazon.Runtime.ErrorType.Unknown
Any idea what I'm doing wrong?
Any comments or suggestions are welcome.
public static async Task<bool> DeleteUserFromAws(string emailId)
{
try
{
AmazonCognitoIdentityProviderClient cognito =
new AmazonCognitoIdentityProviderClient(awsAccessKeyId, awsSecretAccessKey, Region1);
CognitoUserPool cognitoUserPool = new CognitoUserPool(poolId, appClienId, cognito);
AdminGetUserRequest adminGetUserRequest = new AdminGetUserRequest();
adminGetUserRequest.Username = emailId;
adminGetUserRequest.UserPoolId = poolId;
AdminGetUserResponse adminGetUserResponse = await cognito.AdminGetUserAsync(adminGetUserRequest);
var getUserNameByEmaliID = adminGetUserResponse.Username;
AmazonCognitoIdentityProviderClient provider =
new AmazonCognitoIdentityProviderClient(awsAccessKeyId, awsSecretAccessKey, Region1);
AdminDeleteUserRequest request = new AdminDeleteUserRequest();
CancellationToken cancellationToken = default;
request.Username = getUserNameByEmaliID;
request.UserPoolId = poolId;
await provider.AdminDeleteUserAsync(request,cancellationToken);
return true;
}
catch (Exception ex)
{
Logger.log(ex, (Int32)Category.Fatal, (Int32)Priority.High);
throw;
}
}
I am new with Async and await using C# Programming. In WebAPI, we have created two API Controllers one with Async and await Programming and other is without that. We have done load testing using JMeter and we have got following results.
Users Sync Async
100 No Errors No Errors
500 No Errors No Errors
750 No Errors Errors - (59.0 %) - 502 Bad Gateway
763 No Errors Errors
764 No Errors Errors
765 Errors - (0.13 %) - 502 Bad Gateway Errors
1000 Errors Errors
Can you any please explain/suggest which approach is best or how can we proceed ?
API Code :
GetPersonalDetailsController - Async and await Used
public async Task<IHttpActionResult> GET([FromUri] RequestQueryListDTO objAPIRequest)
{
DateTime startResponseTime = DateTime.Now;
Response objResponse = null;
string strResponse = string.Empty;
var HeaderType = Request.Content.Headers.ContentType;
ProductBAL objProductBAL = null;
try
{
if (objAPIRequest != null)
{
Task<Response> tskGetProductDetails = Task<Response>.Run(() =>
{
objProductBAL = new ProductBAL();
return objProductBAL.GetProductDetails(objAPIRequest);
//Business Access Layer Logic calling
});
objResponse = await tskGetProductDetails;
}
else
{
objResponse = new Response();
objResponse.ReturnCode = -1;
objResponse.ReturnMessage = "Missing Parameters.";
}
}
catch (Exception ex)
{
\\ Exception Logging
}
finally
{
objProductBAL = null;
}
objResponse.ResponseTime = Math.Round((DateTime.Now - startResponseTime).TotalMilliseconds).ToString();
if (objResponse.ReturnCode == Convert.ToInt32(General.ReturnCode))
{
return Content<Response>(HttpStatusCode.BadRequest, objResponse);
}
else
{
return Ok(objResponse);
}
}
========================================================================
GetPDPController - Without using Async and await
public IHttpActionResult GET([FromUri] RequestQueryListDTO objAPIRequest)
{
DateTime startResponseTime = DateTime.Now;
Response objResponse = null;
string strResponse = string.Empty;
var HeaderType = Request.Content.Headers.ContentType;
try
{
if (objAPIRequest != null)
{
//Business Access Layer Logic calling
}
else
{
objResponse = new Response();
objResponse.ReturnCode = -1;
objResponse.ReturnMessage = "Missing Parameters.";
}
}
catch (Exception ex)
{
// Exception Logging Code
}
finally
{
objProductBAL = null;
}
objResponse.ResponseTime = Math.Round((DateTime.Now - startResponseTime).TotalMilliseconds).ToString();
if (objResponse.ReturnCode == Convert.ToInt32(General.ReturnCode))
{
return Content<Response>(HttpStatusCode.BadRequest, objResponse);
}
else
{
return Ok(objResponse);
}
}
My suggestion is have two methods, one Async and one not. That way you can test more.
GetProductDetails
GetProductDetailsAsync
you would then need to change the signature of the calling method aka GET
public IHttpActionResult GET([FromUri] RequestQueryListDTO objAPIRequest)
{
var objResponse = new Response();
//check the properties of objAPIRequest
if(bad)
{
//add stuff if you want
return Content<Response>(HttpStatusCode.BadRequest, objResponse);
}
//Business Access Layer Logic calling
//-----------------------
ProductBAL objProductBAL = new ProductBAL();
//you need to change this to async
var productDetails = objProductBAL.GetProductDetails(objAPIRequest);
//-----------------------
return Ok(objResponse);
}
I currently have to provide a sync as async method in my API: Please find the code below. The only problem is that I don’t have a
sync method in the backend. I use Azure.NotificationHub client. That client has only *Async methods. Is my way reasonable?
public PushHubNotificationResult SendPushMessage(string userId, string message)
{
PushHubNotificationResult result = new PushHubNotificationResult();
try
{
result = SendPushMessageAsync(userId, message).GetAwaiter().GetResult();
} catch (Exception ex)
{
result.Status = PushHubNotificationResultType.Error;
result.Error = ex.Message;
result.Exception = ex;
}
return result;
}
public async Task<PushHubNotificationResult> SendPushMessageAsync(string userId, string message)
{
PushHubNotificationResult result = new PushHubNotificationResult();
// EnableTestSend see: https://azure.microsoft.com/en-us/documentation/articles/notification-hubs-push-notification-fixer/#self-diagnose-tips
// Create a new Notification Hub client.
Microsoft.Azure.NotificationHubs.NotificationHubClient hub =
Microsoft.Azure.NotificationHubs.NotificationHubClient.CreateClientFromConnectionString(NotificationHub, NotificationHubName);
// Sending the message so that all template registrations that contain "messageParam"
// will receive the notifications. This includes APNS, GCM, WNS, and MPNS template registrations.
Dictionary<string, string> templateParams = new Dictionary<string, string>();
templateParams["messageParam"] = message;
string userTag = "_UserId:" + userId; // That line sets the IMEI or SerialNo (WLAN only device) == userId to which the push message is sent
try
{
// Send the push notification and log the results.
NotificationOutcome outcome = await hub.SendTemplateNotificationAsync(templateParams, userTag);
result.Status = PushHubNotificationResultType.Success;
foreach (RegistrationResult hubResult in outcome.Results)
{
result.PushNotificationHub = hubResult.ApplicationPlatform;
result.RegistrationId = hubResult.RegistrationId;
result.Outcome = hubResult.Outcome;
}
}
catch (System.Exception ex)
{
result.Status = PushHubNotificationResultType.Error;
result.Error = ex.Message;
result.Exception = ex;
}
return result;
}
thanks for any advice,
Eric
If you want to use sync-over-async, it's very important that you use ConfigureAwait(false) in your async code, otherwise you are very likely to get a deadlock.
NotificationOutcome outcome =
await hub.SendTemplateNotificationAsync(templateParams, userTag).ConfigureAwait(false);
The async method already converts exceptions to PushHubNotificationResultType.Error, why does the sync version do it too?
I'm pretty new to this Async thing. I'm trying to write in to an API using a createasync method. However, for some reason I either get an aggregate exception, or the thread just hangs depending on what I've tried. Here is a code example because I have yet to be able to successfully write in to the Salesforce API. I have been able however, to pull back data using similar operations.
Submit Method where I want this all to take place in my controller:
[System.Web.Http.HttpPost]
public string Submit([FromBody]SurveyFormModel survey)
{
// todo - Validate data and stop if bad data comes in.
var report = BuildReport(survey.Questions);
try
{
var task = Task.Run(async () => { await SendReportToSalesforce(survey); });
task.Wait();
}
catch (Exception ex)
{
ex.GetBaseException();
}
EmailExcel(survey);
return JsonConvert.SerializeObject(report);
}
This is the method I'm using to call my salesforceservice.cs
public async Task SendReportToSalesforce([FromBody] SurveyFormModel survey)
{
SalesforceService service = new SalesforceService();
var auth = service.Authenticate();
var sfSurvey = service.SalesForceMapper(survey, survey.AccountDetails);
var result = await service.SendSurveytoSF(auth.Result, sfSurvey); //.Wait();
Console.WriteLine(result);
}
Also included is the salesforceservice class I use to authenticate as well as the method (SendSurveytoSF) that doesnt seem to be working.
public async Task<ForceClient> Authenticate()
{
//get credential values
var consumerkey = ConfigurationManager.AppSettings["consumerkey"];
var consumersecret = ConfigurationManager.AppSettings["consumersecret"];
var username = ConfigurationManager.AppSettings["username"];
var password = ConfigurationManager.AppSettings["password"];
//create auth client to retrieve token
var auth = new AuthenticationClient();
//get back URL and token
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
try
{
await
auth.UsernamePasswordAsync(consumerkey, consumersecret, username, password,
"https://test.salesforce.com/services/oauth2/token");
}
catch (Exception ex)
{
return null;
}
var instanceUrl = auth.InstanceUrl;
var accessToken = auth.AccessToken;
var apiVersion = auth.ApiVersion;
return new ForceClient(instanceUrl, accessToken, apiVersion);
}
public async Task<Boolean> SendSurveytoSF(ForceClient sfclient, Models.Salesforce.Survey survey)
{
survey.Account__c = "0012200000Ah3zG";
var response = await sfclient.CreateAsync("VBR_Assessment__c", survey);
return response.Id != null;
}
I believe I'm maybe just not calling these methods properly, but at this point I really have no clue as I've tried implementing it a ton of different ways. Thank you for any help in advanced!
UPDATE
This is the exception I'm getting:
A first chance exception of type 'Salesforce.Common.ForceException' occurred in mscorlib.dll
This is the error I get:
One or more errors occurred.
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
at System.Threading.Tasks.Task`1.get_Result()
at myProject.mymethod(Int32[] myIds) in path\MyClass.cs:line 758
And here's that method:
private void mymethod(int[] myIds)
{
var uri = new Uri(string.Format(UriPath, string.Format(MyPath)));
var client = GetHttpClient(uri);
var postModel = new PostModel
{
Ids = myIds,
LastUpdate = NewItem ? null : _lastUpdated
};
if (client != null)
{
var response = client.PostAsJsonAsync(uri, postModel).Result;//this line crashes
if (response.IsSuccessStatusCode)
{
//doSomething
}
}
}
I call a lot of methods like this and all of them work except this one. When it's hit, it takes a lot of time and then this exception is throws. With all of the other methods the error doesn't happen.
This is the inner exception:
Inner.System.Threading.Tasks.TaskCanceledException: A task was canceled.
Here's my GetCLient() method:
private HttpClient GetHttpClient(Uri uri)
{
var handler = new HttpClientHandler
{
CookieContainer = CoockieContainer
};
return new HttpClient(handler)
{
BaseAddress = uri
};
}
Here's the API method:
[HttpPost]
public IList<MyModel> MyAPIMethod(PostModel model)
{
List<MyModel> myTranslations;
using (var db = new myEntities(GetDbConnStrByUser(new GetCookies().GetUserName())))
{
myTranslations = db.tblTranslations.Where(it => model.Ids.Contains(it.id)
&& (!model.Update.HasValue || it.update > model.LastUpdate.Value))
.Select(it => new MyModel
{
Id = it.id,
Name = it.name,
Description = it.desc,
LanguageId = it.language_id
}).ToList();
}
return myTranslations.GroupBy(x => new { x.Id, x.LanguageId }).Select(x => x.First()).ToList();
}
Maybe a timeout occurs.
Fiddler returns this error: The wait operation timed out.
.Result tries to turn Task into T. It synchronously blocks waiting for the task to complete and will only return T if no exceptions occur. The two types of exceptions you should anticipate are OperationCanceledExceptions/TaskCanceledExceptions (when the HTTP request times out or a CancellationToken was used and the token was cancelled--I don't think the latter is applicable here) and general/HTTP-related exceptions.
You're probably running into the HTTP timeout scenario. Is it taking a long time for the exception to get thrown? If not, what does your GetHttpClient method look like? Is it explicitly setting timeouts or cancellation tokens?
If you want to stick with the synchronous approach and not returns Tasks, you should do something like this instead:
try
{
var response = client.PostAsJsonAsync(uri, postModel).Result;//this line crashes
}
catch (OperationCanceledException oce)
{
// Tell the user that the request timed our or you cancelled a CancellationToken
}
catch (Exception exc)
{
// Look at the HttpClient docs and try to catch something more specific. You don't want
// to swallow StackOverflowExceptions or OutOfMemoryExceptions.
}
If you're willing to take the async plunge, this is more what you're looking for:
private async Task mymethodAsync(int[] myIds)
{
var uri = new Uri(string.Format(UriPath, string.Format(MyPath)));
var client = GetHttpClient(uri);
var postModel = new PostModel { ... };
if (client != null)
{
try
{
var response = await client.PostAsJsonAsync(uri, postModel);
if (response.IsSuccessStatusCode)
{
//doSomething
}
}
catch (OperationCanceledException oce)
{
// because timeouts are still possible
}
catch (Exception exc) {
// Because other things can still go wrong too (HTTP 500, parsing errors)
}
}
}
See here for more info on how .Result call works w/HttpClient: What happens while waiting on a Task's Result?