I'm trying to convert a curl request example from an API for Jira into a C# request.
This is the original Curl Request example that JIRA provides:
curl \
-D- \
-u charlie:charlie \
-X GET \
-H "Content-Type: application/json" \
http://localhost:8080/rest/api/2/search?jql=assignee=charlie
Which I've translated into the below code for JIRA:
However the response lines don't work - because I've cobbled together a few examples and got a bit stuck!
var myTask = curlRequestAsync(); // call your method which will return control once it hits await
string result = myTask.Result();
// .Result isn't defined - but I'm not sure how to access the response from my request!
Any help would be appreciated as I'm really stuck!
Full example:
public partial class WebForm2 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
var myTask = curlRequestAsync(); // call your method which will return control once it hits await
string result = myTask.Result();
// wait for the task to complete to continue
}
protected async System.Threading.Tasks.Task curlRequestAsync()
{
try
{
using (var httpClient = new HttpClient())
{
using (var request = new HttpRequestMessage(new HttpMethod("GET"), "http://myurl.co.uk/rest/api/2/search?jql=assignee=bob"))
{
var base64authorization = Convert.ToBase64String(Encoding.ASCII.GetBytes("username:password"));
request.Headers.TryAddWithoutValidation("Authorization", $"Basic {base64authorization}");
var result = await httpClient.SendAsync(request);
return result;
}
}
}
catch (Exception ex)
{
error.InnerText = ex.Message;
}
}
}
you should return Task<System.Net.Http.HttpResponseMessage>
protected async System.Threading.Tasks.Task<HttpResponseMessage> curlRequestAsync()
{
try
{
using (var httpClient = new HttpClient())
{
using (var request = new HttpRequestMessage(new HttpMethod("GET"), "http://myurl.co.uk/rest/api/2/search?jql=assignee=bob"))
{
var base64authorization = Convert.ToBase64String(Encoding.ASCII.GetBytes("username:password"));
request.Headers.TryAddWithoutValidation("Authorization", $"Basic {base64authorization}");
var result = await httpClient.SendAsync(request);
return result;
}
}
}
catch (Exception ex)
{
error.InnerText = ex.Message;
}
}
after that you could access response of your task:
var myTask = curlRequestAsync();
var result = myTask.Result.Content.ReadAsStringAsync().Result;
Due to the async keyword, your methods signature, as "seen by the compiler", within the methods's scope is converted:
protected async Task Foo()
will become
protected void Foo();
To return a value, with the async keyword, you should use this signature:
protected async Task<T> Foo()
which results in
protected T Foo()
As for the caller , the signature stays the same.
On Task, Result is not defined because by its nature it doesn't have a return value from the task. A Task<T> on the other hand has a Result.
So, in order to get an "result", (Result is not defined on Task (Wait is), you should use Task<T>, on which Result is defined.
In your case you should change the signature to:
protected async System.Threading.Tasks.Task<WhatEverTypeYouAreReturning> curlRequestAsync()
You will now able to get the Result or await the call if you are in an async scope. The latter is preferred since it will keep your method async which has some benefits regarding to the use of resources.
Related
I have a PostAsync method in an internal part of my code that doesn't seem to ever return a response. However, I use it synchronously via .GetAwaiter().GetResult(). The target framework is net45.
public async Task<TResponse> PostAsync<TResponse, TRequest>(string method, TRequest body)
{
_logger.Log($"Method {method}, body {JsonConvert.SerializeObject(body)} on url {_configuration.ApiUrl}");
using (var customDelegatingHandler = new HMACDelegatingHandler(_configuration, _apiId))
{
using (var client = new HttpClient(customDelegatingHandler))
{
var response = await client.PostAsync($"{_configuration.ApiUrl}/{method}",
new StringContent(JsonConvert.SerializeObject(body), Encoding.UTF8, "application/json"));
if (response.StatusCode == HttpStatusCode.OK)
{
var content = await response.Content.ReadAsStringAsync();
return JsonConvert.DeserializeObject<TResponse>(content);
}
else
{
await Log(body, response);
}
return default;
}
}
}
What I do is call the PostAsync in another method:
public async Task<decimal> GetBalance(Request request)
{
// = new MyCustomClient...
QueryFundsResponse response = await customClient.PostAsync<Response, Request>("testAction", request);
if (response == default)
return 0.0m;
return response.Amount;
}
Then, finally at the very top of the flow, I call the GetBalance method like this:
var sw = new Stopwatch();
sw.Start();
var balance = _provider
.GetBalance(request)
.ConfigureAwait(false)
.GetAwaiter()
.GetResult();
sw.Stop();
_logger.Log($"GetBalance -> method duration: { sw.ElapsedMilliseconds }");
I don't see the log in my logs at all, and I don't seem to ever get a response or any code executed after the .GetAwaiter().GetResult(). Switching the last block of code to be asynchronous and await the GetBalance() method is not really an option for me, sadly.
I am unable to figure out why nothing is changing, even after using the .ConfigureAwait(false) method.
You're experiencing the common deadlock that happens when you block on asynchronous code (described in detail on my blog). There are a variety of ways to get around it, but they're all hacks and none of them work in every situation.
In your case, I'd say either use the direct blocking hack or use the boolean argument hack.
The direct blocking hack requires you to use ConfigureAwait(false) everywhere. Note that your current code only uses ConfigureAwait(false) where it doesn't do anything; ConfigureAwait configures the await, so it needs to go where the awaits are. All of them.
The boolean argument hack means that your code will take a bool parameter that determines whether it executes synchronously or asynchronously. Note that HttpClient (for now) has an async-only API, so your custom delegating handler will need to support direct blocking, using ConfigureAwait(false). Similarly, Log will either need a synchronous equivalent or also support direct blocking. Your code would end up looking something like this:
public Task<TResponse> PostAsync<TResponse, TRequest>(string method, TRequest body) => PostCoreAsync(method, body, sync: false);
public TResponse Post<TResponse, TRequest>(string method, TRequest body) => PostCoreAsync(method, body, sync: true).GetAwaiter().GetResult();
private async Task<TResponse> PostCoreAsync<TResponse, TRequest>(string method, TRequest body, bool sync)
{
_logger.Log($"Method {method}, body {JsonConvert.SerializeObject(body)} on url {_configuration.ApiUrl}");
using (var customDelegatingHandler = new HMACDelegatingHandler(_configuration, _apiId))
{
using (var client = new HttpClient(customDelegatingHandler))
{
var responseTask = client.PostAsync($"{_configuration.ApiUrl}/{method}",
new StringContent(JsonConvert.SerializeObject(body), Encoding.UTF8, "application/json"));
var response = sync ? responseTask.GetAwaiter().GetResult() : await responseTask;
if (response.StatusCode == HttpStatusCode.OK)
{
var content = sync ? response.Content.ReadAsStringAsync().GetAwaiter().GetResult() : await response.Content.ReadAsStringAsync();
return JsonConvert.DeserializeObject<TResponse>(content);
}
else
{
var logTask = Log(body, response);
if (sync)
logTask.GetAwaiter().GetResult();
else
await logTask;
}
return default;
}
}
}
public Task<decimal> GetBalanceAsync(Request request) => GetBalanceCoreAsync(request, sync: false);
public decimal GetBalance(Request request) => GetBalanceCoreAsync(request, sync: true).GetAwaiter().GetResult();
private async Task<decimal> GetBalanceCoreAsync(Request request, bool sync)
{
// = new MyCustomClient...
QueryFundsResponse response = sync ?
customClient.Post<Response, Request>("testAction", request) :
await customClient.PostAsync<Response, Request>("testAction", request);
if (response == default)
return 0.0m;
return response.Amount;
}
var sw = new Stopwatch();
sw.Start();
var balance = _provider
.GetBalance(request);
sw.Stop();
_logger.Log($"GetBalance -> method duration: { sw.ElapsedMilliseconds }");
Currently working with the outlook api, even tough I usually work with the outlook library acquired via Nuget; I have reached a limitation where I am not able to accept event invitations. So I proceeded in making a a restful call out to the the outlook api. However, when I am making the call I am getting the following message {"error":{"code":"InvalidMethod","message":"An action can only be invoked as a 'POST' request."}} when executing the call.
Bad Code
class Program
{
static void Main(string[] args)
{
var testAccept = ExecuteClientCall.AcceptEvent().Result;
}
public static async Task<bool> AcceptEvent()
{
AuthenticationContext authenticationContext = new AuthenticationContext(CrmPrototype.Helpers.AuthHelper.devTenant);
try
{
var token = await GetTokenHelperAsync(authenticationContext, CrmPrototype.Helpers.AuthHelper.OutlookAuthenticationEndpoint);
string requestUrl = "https://outlook.office.com/api/v2.0/Users/***#nowwhere.com/events('AAQkAGZiNDQxZTVkLWQzZjEtNDdjNy04OTc4LTM4NmNjM2JiOTRjNAAQAFpV0CnWR0FIpWFYRtszPHU=')/accept";
HttpClient hc = new HttpClient();
hc.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
var method = new HttpMethod("POST");
var request = new HttpRequestMessage(method, requestUrl)
{
Content = new StringContent("{SendResponse: true}", Encoding.UTF8, "application/json")
};
HttpResponseMessage hrm = await hc.GetAsync(requestUrl);
if (hrm.IsSuccessStatusCode)
{
string jsonresult = await hrm.Content.ReadAsStringAsync();
var stophere = 0;
}
else
{
return false;
}
return true;
}
catch (Exception ex)
{
throw;
}
}
}
Maybe the reason is that you called
hc.GetAsync(requestUrl);
The doc said that this method:
Sends a GET request to the specified Uri as an asynchronous operation.
Try:
PostAsync(Uri, HttpContent)
https://msdn.microsoft.com/en-us/library/system.net.http.httpclient(v=vs.118).aspx
Hope this help you.
Your variable request contains an HttpRequestMessage object that you have created, but your code presently doesn't do anything with it.
Try replacing the line
HttpResponseMessage hrm = await hc.GetAsync(requestUrl);
(which, as pointed out by the other answer, makes a GET request), with
HttpResponseMessage hrm = await hc.SendAsync(request);
After considering this interesting answer HttpClient.GetAsync(...) never returns..., I still have a situation where my HttpClient is not returning when I use await (sample code below). In addition. I use this helper routine from both asp.net MVC5 Controllers (UI-driven) and the WebApi. What can I do to:
Use await instead of the (dreaded) .Result and still have this function return?
Reuse this same routine from both MVC Controllers and WebApi?
Apparently, I should replace the .Result with .ConfigureAwait(false) but this seems to contradict with the fact that "Task4" in the post cited above works fine with an await httpClient.GetAsync. Or do I need separate routines for Controller and WebApi cases?
public static async Task<IEnumerable<TcMarketUserFullV1>> TcSearchMultiUsersAsync(string elasticQuery)
{
if (string.IsNullOrEmpty(elasticQuery)) return null;
IEnumerable<TcMarketUserFullV1> res = null;
using (var hclient = new HttpClient())
{
hclient.BaseAddress = new Uri("https://addr.servicex.com");
hclient.DefaultRequestHeaders.Accept.Clear();
hclient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
hclient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer",
CloudConfigurationManager.GetSetting("jwt-bearer-token"));
// Why does this never return when await is used?
HttpResponseMessage response = hclient.GetAsync("api/v2/users?q=" + elasticQuery + "&search_engine=v2").Result;
if (response.IsSuccessStatusCode)
{
var content = await response.Content.ReadAsStringAsync();
res = JsonConvert.DeserializeObject<TcMarketUserFullV1[]>(content).AsEnumerable();
}
else{log.Warn("...");}
}
return res;
}
UPDATE: My call chain, which starts with a Telerik Kendo Mvc.Grid DataBinding call is as follows:
[HttpPost]
public async Task<ActionResult> TopLicenseGrid_Read([DataSourceRequest]DataSourceRequest request)
{
var res = await GetLicenseInfo();
return Json(res.ToDataSourceResult(request)); // Kendo.Mvc.Extensions.DataSourceRequest
}
Then:
private async Task<IEnumerable<CsoPortalLicenseInfoModel>> GetLicenseInfo()
{
...
// Never returns
var qry = #"app_metadata.tc_app_user.country:""DE""";
return await TcSearchMultiUsersAsync(qry);
}
Then, the routine shown in full above but now WITHOUT the .Result:
public static async Task<IEnumerable<TcMarketUserFullV1>> TcSearchMultiUsersAsync(string elasticQuery)
{
if (string.IsNullOrEmpty(elasticQuery)) return null;
IEnumerable<TcMarketUserFullV1> res = null;
using (var hclient = new HttpClient())
{
hclient.BaseAddress = new Uri("https://addr.servicex.com");
hclient.DefaultRequestHeaders.Accept.Clear();
hclient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
hclient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer",
CloudConfigurationManager.GetSetting("jwt-bearer-token"));
// This now returns fine
HttpResponseMessage response = hclient.GetAsync("api/v2/users?search_engine=v2&q=" + elasticQuery");
if (response.IsSuccessStatusCode)
{
// This returns my results fine too
var content = await response.Content.ReadAsStringAsync();
// The following line never returns results. When debugging, everything flows perfectly until I reach the following line, which never
// returns and the debugger returns me immediately to the top level HttpPost with a result of null.
res = JsonConvert.DeserializeObject<TcMarketUserFullV1[]>(content).AsEnumerable();
}
else{log.Warn("...");}
}
return res;
}
You need to await everything. It's not enough that you await on one of them, you need to await on all of them:
This:
HttpResponseMessage response = hclient.GetAsync(
"api/v2/users?q=" + elasticQuery + "&search_engine=v2").Result;
Should be:
HttpResponseMessage response = await hclient.GetAsync(
"api/v2/users?q=" + elasticQuery + "&search_engine=v2");
It is enough to have one blocking call to .Result in order to deadlock. You need "async all the way".
I have this async method:
public async Task<RES> PostAsync<RES>(string url, string content) where RES : new()
{
using (var client = new HttpClient())
{
HttpResponseMessage message = await client.PostAsync(url, new StringContent(content, Encoding.UTF8, "application/json"));
var readAsStringAsync = await message.Content.ReadAsStringAsync();
return await readAsStringAsync.FromJsonAsync<RES>(mySerializerSettings);
}
}
Where FromJsonAsync is implemented as an extension method:
public async static Task<T> FromJsonAsync<T>(this string data, JsonSerializerSettings settings) where T : new()
{
return (T)(await JsonConvert.DeserializeObjectAsync<T>(data, settings));
}
Now I want to add a regular synchronous Post method and I thought the implementation would be:
public RES Post<RES>(string url, string content) where RES : new()
{
return PostAsync<RES>(url, content).Result;
}
But this doesn't really work. I see that the request is sent via a Http sniffer and I get a response back, but I get stuck when debugging and can't continue.
BTW, this does work (with Result instead of await):
public RES Post<RES>(string url, string content) where RES : new()
{
using (var client = new HttpClient())
{
HttpResponseMessage message = client.PostAsync(url, new StringContent(content, Encoding.UTF8, "application/json")).Result;
var readAsStringAsync = message.Content.ReadAsStringAsync().Result;
return readAsStringAsync.FromJson<RES>(mySerializerSettings);
}
}
Where FromJson is implemented as an extension method:
public static T FromJson<T>(this string data, JsonSerializerSettings settings) where T : new()
{
return (T)JsonConvert.DeserializeObject<T>(data, settings);
}
The application is a web backend (WebApi).
What am I doing wrong?
You probably have a deadlock on your hands.
Asp.net uses a SynchronizationContext to post continuations back to the request context. If the context is blocked (like it is in your case on PostAsync<RES>(url, content).Result) then the continuation can't be executed and so the async method can't complete and you have a deadlock.
You can avoid it by using ConfigureAwait(false):
public async Task<RES> PostAsync<RES>(string url, string content) where RES : new()
{
using (var client = new HttpClient())
{
HttpResponseMessage message = await client.PostAsync(url, new StringContent(content, Encoding.UTF8, "application/json"));
var readAsStringAsync = await message.Content.ReadAsStringAsync().ConfigureAwait(false);
return await readAsStringAsync.FromJsonAsync<RES>(mySerializerSettings).ConfigureAwait(false);
}
}
But it's better to just avoid blocking synchronously on async code to begin with and having two different versions for sync and async.
Although possible, I wouldn't use the answer provided by #i3arnon. Generally, you shouldn't block on async code. Although ConfigureAwait(false) does work, it can lead to confusion in your code-base where other developers may also end up blocking using .Result, without using ConfigureAwait or understanding the implications of that.
Instead, expose synchronous methods which are really synchronous:
public RES Post<RES>(string url, string content) where RES : new()
{
using (var client = new WebClient())
{
client.Headers[HttpRequestHeader.ContentType] = "application/json";
var result = client.UploadString(url, content);
return JsonConvert.DeserializeObject<RES>(result, jsonSerializerSettings);
}
}
It seems you have a non-async function and you want to start a task that will call PostAsync and wait for this task to finish and return the result of the Task. Is this your problem?
To start a Task, use Task.Run( () => ...);
To wait for the Task use Task.Wait(...);
To see if the task stopped because of an exception: Task.IsFaulted
The result of the task is in Task.Result
Your code could be:
public async Task<RES> PostAsync<RES>(string url, string content) where RES : new()
{
// start the task that will call PostAsync:
var postTask = Task.Run( () => PostAsync(url, content));
// while this task is running you can do other things
// once you need the result: wait for the task to finish:
postTask.Wait();
// If needed check Task.IsFaulted / Task.IsCanceled etc. to check for errors
// the returned value is in Task.Result:
return postTask.Result;
}
I'm using the following code to get an endpoint and write it to a cache:
public async Task UpdateCacheFromHttp(string Uri)
{
if (string.IsNullOrEmpty(Uri))
return;
var httpClient = new HttpClient();
var response = await httpClient.GetAsync(Uri);
if ((response != null) && (response.IsSuccessStatusCode))
{
var responseStream = await response.Content.ReadAsStreamAsync();
WriteToCache(responseStream);
}
}
The code is running on IIS.
If the endpoint can't be reached I'd expect GetAsync to throw an exception. Even with a Try-Catch, it never seems to fail. GetAsync never returns (I tried a 5 second timeout on the HttpClient, still didn't return).
This does throw an exception:
public Task UpdateCacheFromHttp(string Uri)
{
var updateCacheTask = Task.Factory.StartNew(new Action(() =>
{
if (string.IsNullOrEmpty(Uri))
return;
var httpClient = new HttpClient();
var response = httpClient.GetAsync(Uri).Result;
if (response.IsSuccessStatusCode)
{
var responseStream = response.Content.ReadAsStreamAsync().Result;
WriteToCache(responseStream);
}
}));
return updateCacheTask;
}
I get the expected "Unable to connect to the remote server".
I suspect it has something to do with the code running in IIS, but why? How do I get it to properly throw the exception without the need to start a new task?
My intuition tells me that you're calling Wait or Result further up your call stack.
If that is correct, then you're causing a deadlock, as I explain on my blog.
As I encountered the same behaviour with no Exception being thrown, I created a sample to demonstrate the problem with a possible solution:
using System;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
namespace Exam
{
public static class Program
{
private static async Task<string> GetWebPage(string uri)
{
var httpClient = new HttpClient();
var response = await httpClient.GetAsync(new Uri(uri, UriKind.Absolute), HttpCompletionOption.ResponseContentRead);
return await response.Content.ReadAsStringAsync();
}
public static void Main(string[] args)
{
try
{
// These two lines do not work - i.e. it terminates the application without any exception being thrown...
//string s = await GetWebPage(#"https://www.dwd.de/DE/leistungen/klimadatendeutschland/klimadatendeutschland.html");
//Console.WriteLine(s);
// This works:
Task<string> getPageTask = GetWebPage(#"https://www.dwd.de/DE/leistungen/klimadatendeutschland/klimadatendeutschland.html");
getPageTask.Wait();
if (getPageTask.IsCompleted)
Console.WriteLine(getPageTask.Result);
}
catch (AggregateException aex)
{
aex.InnerExceptions.AsParallel().ForAll(ex => Console.WriteLine(ex));
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
Console.ReadKey();
}
}
}
When you additionally change the URI to something like #"invalid https://...." you will retrieve the AggregateException.
Hope, it helps anyone :-)