I have seen similar questions asked but none that seem to help me with my issue so please bear with me.
I have a WebAPI controller method that is defined as such:
[HttpPost]
[Route("")]
public HttpResponseMessage CreateMyObject(MyObjectRequest myObject)
{
MyObject o;
try
{
o = _serviceFactory.GetInstance().CreateMyObject(myObject);
}
catch (Exception ex)
{
ex.WriteToLog();
throw ApiHelper.CreateResponseException(HttpStatusCode.InternalServerError, ex);
}
var response = Request.CreateResponse(HttpStatusCode.Created, o);
var uri = Url.Link("GetMyObjectById", new { myObjectId = o.MyObjectId.ToString() });
response.Headers.Location = new Uri(uri);
return response;
}
Say, MyObject contains two properties,
public MyObject
{
public Guid MyObjectId;
public string MyObjectName
}
A client was written to call these controller methods in a WPF application. Here is the client method that is being used:
public HttpResponseMessage CreateQuote(MyObjectRequest myObject)
{
var hashtable = new Hashtable
{
{"myObject", myObject}
};
var task = GetResponse("", hashtable);
var response = task.Result;
return response;
}
protected async Task<HttpResponseMessage> GetResponse(string path, Hashtable parameters)
{
var response = await GetAsync(BuildRequestUri(path, parameters)).ConfigureAwait(false);
return response.IsSuccessStatusCode ? response : new HttpResponseMessage();
}
protected async Task<HttpResponseMessage> GetResponse(string path)
{
return await GetResponse(path, null);
}
The controller and supporting client code was not written by me and was already in the system. I am just consuming this in the WPF application. Now, I am trying to call the controller method via the client in the application and get the MyObject from the response so that I can access the MyObjectId that has been created and set. I have tried some of the other responses to similar questions but have not even seen some of the methods that are called on the response in order to get the information. Here is the first part of the call to the client that I have in the application:
var httpResponse = ApplicationService.CreateMyObject(myObjectRequest);
The application service simply injects the client into the constructor and allows me to call the CreateMyObject method. Is there any insight that can be given to me on how I should be getting the MyObject object out of the response?
I'm still a little new to web api as well, but I'm currently working with it on a project. Give the following code a try:
MyObject myObject;
if (response.IsSuccessStatusCode)
{
// Parse the response body. Blocking!
myObject = response.Content.ReadAsAsync<MyObject>().Result;
}
So you could theoretically change your method like this (may not be exactly what you want):
public MyObject CreateQuote(MyObjectRequest myObject)
{
var hashtable = new Hashtable
{
{"myObject", myObject}
};
var task = GetResponse("", hashtable);
var response = task.Result;
MyObject newObject;
if (response.IsSuccessStatusCode)
{
// Parse the response body. Blocking!
newObject= response.Content.ReadAsAsync<MyObject>().Result;
}
return newObject; // instead of response
}
Related
I have an endpoint which is used to create an item. The controller calls the service which creates the item, makes some changes on the db and db returns data based on the procedure. The db returns a json like response, but is not always the same, so I have to adjust on the backend so that I can formalize the response type.
The problem is that create item service is asynchronous and I need to be able to await the response so I can make a new response based on that. How can I await the response and that I get from db client and then return data based on that.
This is my Action and I want to be able to serialize async response from service
[HttpPost]
public IActionResult CreateItem([FromBody] InputModel item)
{
var jsonString = _itemService.CreateItem(item);
ResponseModel? response = JsonSerializer.Deserialize<ResponseModel>(jsonString);
return new ObjectResult(response.Response) { StatusCode = response.StatusCode };
}
The default response model
public class ResponseModel
{
public string Response { get; set; }
public int StatusCode { get; set; }
}
Create Item service, which makes the post request to the client and it has to be async.
Depending on the status code that is coming from the client, I want to be able to set my action status code as well.
public async Task<string> CreateItem(InputModel item)
{
if (item.VersionType != 1)
{
return new { Response = "Incorrect data", StatusCode = 400 }.ToString()!;
}
var json = JsonSerializer.Serialize(item);
var data = new StringContent(json, Encoding.UTF8, "application/json");
var response = await client.PostAsync(url, data);
var content = await response.Content.ReadAsStringAsync();
return content;
}
You can make your action method async and then await the method call _itemService.CreateItem for it :
[HttpPost]
public async Task<IActionResult> CreateItem([FromBody] InputModel item)
{
var jsonString = await _itemService.CreateItem(item);
ResponseModel? response = JsonSerializer.Deserialize<ResponseModel>(jsonString);
return new ObjectResult(response.Response) { StatusCode = response.StatusCode };
}
Now your action method would asyncrounously wait for the result from CreateItem and when it returs result, it will continue executing further and send the deserialized response back to client.
The client and a generic method for the API requests are created here:
public class Client : IDisposable
{
private HttpClient _client;
private void CreateClient()
{
_client = new HttpClient();
_client.DefaultRequestHeaders.Accept.Clear();
_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
_client.DefaultRequestHeaders.Add("KEY", token);
}
public void Dispose() => _client?.Dispose();
public enum Method { GET, POST, PUT, DELETE }
public HttpResponseMessage Request(string url, Method method, object data, HttpContent request)
{
if (data != null)
request = new StringContent(Serialize(data), Encoding.UTF8, "application/json");
switch (method)
{
case Method.POST: return _client.PostAsync(url, request).Result;
case Method.PUT: return _client.PutAsync(url, request).Result;
case Method.DELETE: return _client.DeleteAsync(url).Result;
default: return _client.GetAsync(url).Result;
}
}
public Task<HttpResponseMessage> RequestAsync(string url, Method method, object data, HttpContent request)
{
if (data != null)
request = new StringContent(Serialize(data), Encoding.UTF8, "application/json");
switch (method)
{
case Method.GET: return _client.GetAsync(url);
case Method.POST: return _client.PostAsync(url, request);
case Method.PUT: return _client.PutAsync(url, request);
case Method.DELETE: return _client.DeleteAsync(url);
default: return _client.GetAsync(url);
}
}
public string Post(string url, object data) =>
Request(url, Method.POST, data, null).Content.ReadAsStringAsync().Result;
public Task<HttpResponseMessage> PostAsync(string url, object data) =>
RequestAsync(url, Method.POST, data, null);
//UTILS
private static string Serialize(object data) =>
data == null
? string.Empty
: JsonConvert.SerializeObject(data, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });
}
I'm trying to call these methods to specific classes, to simplify the usage of it for the customer. For example, to create a new checkout for a transaction in a credit card:
public class Checkout : SDK
{
private static Client client;
public Checkout() => client = new Client();
public static async Task Credit(object data) =>
await client.PostAsync(url, data);
}
The request needs to be mounted based on a few models, that can have this structure and I'm trying to generate it in a simple way, like this:
public async Task Test()
{
var transaction = new Transaction
{
PaymentMethod = new PaymentMethod { Code = "1" },
Application = "Test",
Vendor = "Name",
Customer = new Customer
{
//Customer details...
},
Products = new List<TransactionProduct>
{
//Products...
}
};
var teste = Checkout.Credit(transaction);
Console.WriteLine(teste);
}
And all I get as return is:
System.Threading.Tasks.Task`1[System.Threading.Tasks.VoidTaskResult]
Id = 1, Status = WaitingForActivation, Method = "{null}", Result = "{Not yet computed}"
I've tried to add await for the Checkout.Credit call, but I get:
CS0815 Test C# Cannot assign void to an implicitly-typed variable
Unit testing this with a simple HttpClient requests works like a charm, but I'm not being able to identify the problem on my project structure, so any help will be very much appreciated.
Task is the return type for an async method that does not have a return value.
Or, to put it another way, async wraps T values into Task<T> (or void returns into Task), and await unwraps those values. Since Credit returns Task, the type of the expression Checkout.Credit(transaction) is Task, and the type of the expression await Checkout.Credit(transaction) is void. And you cannot assign void to var teste; that's what the compiler error is saying.
To fix this, give your async method return types. In particular:
public static async Task<HttpResponseMessage> Credit(object data) =>
await client.PostAsync(url, data);
On a side note, this is quite strange:
public string Post(string url, object data) => ...;
public Task<HttpResponseMessage> PostAsync(string url, object data) => ...;
Usually, if you have a Method and a MethodAsync where Method has some return type TResult, then MethodAsync will have the return type Task<TResult>, not Task<SomeCompletelyDifferentType>. A more natural API would be something like this:
public async Task<HttpResponseMessage> PostAsync(string url, object data)
{
var result = await Request(url, Method.POST, data, null);
return await result.Content.ReadAsStringAsync();
}
I studied over the Internet regarding Task Async method but cannot seem to find an approach to assign my return value in Task Async to another object. The first method is to prepare HTTP Request header and Uri.
public static async Task MainAsync()
{
string token = await AuthHelper.AcquireToken(tenantId, clientId, clientSecret);
using (var client = new HttpClient())
{
client.DefaultRequestHeaders.Add("Authorization", "Bearer " + token);
client.BaseAddress = new Uri("https://foo.net");
await GetValue(client);
}
}
The second method is to use GetAsync to call to an API to get the JSON and the two last lines I extract only value from the "Value" field in the JSON body.
public static async Task<String> GetValue(HttpClient client)
{
string url = $"/mykey/key01";
using (var httpResponse = await client.GetAsync(url))
{
httpResponse.EnsureSuccessStatusCode();
string responsContent = await httpResponse.Content.ReadAsStringAsync();
JObject json = JObject.Parse(responsContent);
string value = json["value"].ToString();
return value;
}
}
Now I would like to use this value to assign to another object, but not sure how to do so. I managed to return the valid value. Is it possible to retrieve the value from another method or even different class?
[Updated] The main function is:
static void Main(string[] args)
{
try
{
MainAsync().Wait();
}
catch (Exception e)
{
Console.WriteLine(e.GetBaseException().Message);
}
}
Update
To be more clear. The HTTP response message is a JSON format and I can return the value from Value property in this JSON. Now how I can to reuse the value from an external method or class
I'm not sure exactly what you are trying to achieve. And there would be thorough debates about your architecture, you can do something like this..
Update
Because your MainAsync is static it can be called form anywhere.
You just need to modify it a bit to return your result as follows :
public static async Task<string> MainAsync()
{
...
return await GetValue(client);
...
And somewhere else
public class MyAwesomeClass
{
public async Task DoMagic()
{
var newValueOfSomething = await MainAsync();
// hilarity ensues
}
}
You can Make it more generic and useful, something like below :
Your initial method can be changes to :
public async Task<T> GetContentAsync<T>(HttpClient client)
{
string url = $"/mykey/key01";
using (var httpResponse = await client.GetAsync(url))
{
httpResponse.EnsureSuccessStatusCode();
string responsContent = await httpResponse.Content.ReadAsStringAsync();
return Deserialize<T>(json);
}
}
private T Deserialize<T>(string json)
{
return JsonConvert.DeserializeObject<T>(json, SerializationSettings);
}
You can now call method like :
var person = await GetContentAsync<Person>(/*http client*/)
Previously i handled all my http requests in a single class but i would like to move the http login functionality to a different class but now i cant access the http client response.IsSuccessStatusCode
this is my original code whic works
var http = new HttpClient();
var url = String.Format(shared.AppDetails.domainurl+"/v2auth/default/login");
var response2 = await http.PostAsync(url, credentials);
if (response.IsSuccessStatusCode)
{
//do after login stuff
}
Now i would like to move the login logic to a different class that is in a different folder(auth->dbhelpers)
class LoginHttp
{
public static async Task<object> loginAsync(String username, String password)
{
var values = new Dictionary<string, string>
{
{ "username",username },
{ "password", password }
};
var credentials = new FormUrlEncodedContent(values);
var http = new HttpClient();
var url = String.Format(shared.AppDetails.domainurl + "/v2auth/default/login");
var response = await http.PostAsync(url, credentials);
return response;
}
}
So am now trying to access the returned response via
var responsefromhttplogin = auth.dbhelpers.AuthHttp.loginAsync(login_username.Text, login_password.Password);
if (responsefromhttplogin .IsSuccessStatusCode) //this fails
{
//do after login stuff
}
How can i get the retrned response be of type HttpClient again?
Am getting an error of
Task<Objct> does not contain defination for IsSuccessStatusCode
Make your loginAsync method return Task instead. Currently you are returning an object, then you will have access to the IsSuccessStatusCode
class LoginHttp{
public static async Task<HttpResponseMessage> loginAsync(String username, String password)
{
var values = new Dictionary<string, string>
{
{ "username",username },
{ "password", password }
};
var credentials = new FormUrlEncodedContent(values);
var http = new HttpClient();
var url = String.Format(shared.AppDetails.domainurl + "/v2auth/default/login");
var response = await http.PostAsync(url, credentials);
return response;
}
}
You also need to use await in your calling method, otherwise you get a Task back
var responsefromhttplogin = await auth.dbhelpers.AuthHttp.loginAsync(login_username.Text, login_password.Password);
if (responsefromhttplogin.IsSuccessStatusCode)
{
//do after login stuff
}
Try to change your code to await async method like this:
var responsefromhttplogin = await auth.dbhelpers.AuthHttp.loginAsync(login_username.Text, login_password.Password);
if (responsefromhttplogin.IsSuccessStatusCode)
{
//do after login stuff
}
Now after you add await this responsefromhttplogin.IsSuccessStatusCode should be accessible.
And also change your method to return Task<HttpResponseMessage> instead of Task<object>
You are returning Task<object> from loginAsync(), to access the result of the task you can use Task.Result.
I would consider to narrow down the type that you are returning from object to HttpResponseMessage.
Judging from your code, you are returning a Task<object>
You should either cast the return response; as return (HttpResponseMessage) response;
Or change the return type to be Task<HttpResponseMessage>
Relevant documentation
My Question: How do I do this?
So, I hadn't touched anything .Net in about 6 years until this week. There's a lot that I've forgotten and even more that I never knew and while I love the idea of the async/await keywords, I'm having a slight problem implementing the following requirements for a client's API implementation:
The ServerAPI class has a method for each of the API methods, taking appropriate input parameters (e.g. the method Login takes in an id and a password, makes the API call and returns the result to the caller).
I want to abstract away the JSON so that my API methods return the actual object you're fetching (e.g. the Login method above returns a User object with your auth token, uid, etc.)
Some API methods return a 204 on success or no meaningful content (not meaningful in my usecase maybe I only care about success/failure), for these I'd like to return either a bool (true = success) or the status code.
I'd like to keep the async/await (or equivalent) design, because it seems to really work well so far.
For some methods, I might need to just return the HttpResponseMessage object and let the caller deal with it.
This is roughly what I have so far and I'm not sure how to make it compliant with the above OR whether I'm even doing this right. Any guidance is appreciated (flaming, however, is not).
// 200 (+User JSON) = success, otherwise APIError JSON
internal async Task<User> Login (string id, string password)
{
LoginPayload payload = new LoginPayload() { LoginId = id, Password = password};
var request = NewRequest(HttpMethod.Post, "login");
JsonPayload<LoginPayload>(payload, ref request);
return await Execute<Account>(request, false);
}
// 204: success, anything else failure
internal async Task<Boolean> LogOut ()
{
return await Execute<Boolean>(NewRequest(HttpMethod.Delete, "login"), true);
}
internal async Task<HttpResponseMessage> GetRawResponse ()
{
return await Execute<HttpResponseMessage>(NewRequest(HttpMethod.Get, "raw/something"), true);
}
internal async Task<Int32> GetMeStatusCode ()
{
return await Execute<Int32>(NewRequest(HttpMethod.Get, "some/intstatus"), true);
}
private async Task<RESULT> Execute<RESULT>(HttpRequestMessage request, bool authenticate)
{
if (authenticate)
AuthenticateRequest(ref request); // add auth token to request
var tcs = new TaskCompletionSource<RESULT>();
var response = await client.SendAsync(request);
// TODO: If the RESULT is just HTTPResponseMessage, the rest is unnecessary
if (response.IsSuccessStatusCode)
{
try
{
// TryParse needs to handle Boolean differently than other types
RESULT result = await TryParse<RESULT>(response);
tcs.SetResult(result);
}
catch (Exception e)
{
tcs.SetException(e);
}
}
else
{
try
{
APIError error = await TryParse<APIError>(response);
tcs.SetException(new APIException(error));
}
catch (Exception e)
{
tcs.SetException(new APIException("Unknown error"));
}
}
return tcs.Task.Result;
}
This is the APIError JSON structure (it's the status code + a custom error code).
{
"status": 404,
"code":216,
"msg":"User not found"
}
I would prefer to stay with System.Net, but that's mostly because I don't want to switch all my code over. If what I want is easier done in other ways then it's obviously worth the extra work.
Thanks.
Here is an example of how I've done it using MVC API 2 as backend. My backend returns a json result if the credentials are correct. UserCredentials class is the exact same model as the json result. You will have to use System.Net.Http.Formatting which can be found in the Microsoft.AspNet.WebApi.Client NugetPackage
public static async Task<UserCredentials> Login(string username, string password)
{
string baseAddress = "127.0.0.1/";
HttpClient client = new HttpClient();
var authorizationHeader = Convert.ToBase64String(Encoding.UTF8.GetBytes("xyz:secretKey"));
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", authorizationHeader);
var form = new Dictionary<string, string>
{
{ "grant_type", "password" },
{ "username", username },
{ "password", password },
};
var Response = await client.PostAsync(baseAddress + "oauth/token", new FormUrlEncodedContent(form));
if (Response.StatusCode == HttpStatusCode.OK)
{
return await Response.Content.ReadAsAsync<UserCredentials>(new[] { new JsonMediaTypeFormatter() });
}
else
{
return null;
}
}
and you also need Newtonsoft.Json package.
public class UserCredentials
{
[JsonProperty("access_token")]
public string AccessToken { get; set; }
[JsonProperty("token_type")]
public string TokenType { get; set; }
[JsonProperty("expires_in")]
public int ExpiresIn { get; set; }
//more properties...
}
i would use a Deserializer.
HttpResponseMessage response = await client.GetAsync("your http here");
var responseString = await response.Content.ReadAsStringAsync();
[Your Class] object= JsonConvert.DeserializeObject<[Your Class]>(responseString.Body.ToString());
So, first to address the you need Newtonsoft.Json comments, I really haven't felt the need yet. I've found the built in support to work well so far (using the APIError Json in my original question:
[DataContract]
internal class APIError
{
[DataMember (Name = "status")]
public int StatusCode { get; set; }
[DataMember (Name = "code")]
public int ErrorCode { get; set; }
}
I have also defined a JsonHelper class to (de)serialize:
public class JsonHelper
{
public static T fromJson<T> (string json)
{
var bytes = Encoding.Unicode.GetBytes (json);
using (MemoryStream mst = new MemoryStream(bytes))
{
var serializer = new DataContractJsonSerializer (typeof (T));
return (T)serializer.ReadObject (mst);
}
}
public static string toJson (object instance)
{
using (MemoryStream mst = new MemoryStream())
{
var serializer = new DataContractJsonSerializer (instance.GetType());
serializer.WriteObject (mst, instance);
mst.Position = 0;
using (StreamReader r = new StreamReader(mst))
{
return r.ReadToEnd();
}
}
}
}
The above bits I already had working. As for a single method that would handle each request execution based on the type of result expected while it makes it easier to change how I handle things (like errors, etc), it also adds to the complexity and thus readability of my code. I ended up creating separate methods (all variants of the Execute method in the original question:
// execute and return response.StatusCode
private static async Task<HttpStatusCode> ExecuteForStatusCode (HttpRequestMessage request, bool authenticate = true)
// execute and return response without processing
private static async Task<HttpResponseMessage> ExecuteForRawResponse(HttpRequestMessage request, bool authenticate = true)
// execute and return response.IsSuccessStatusCode
private static async Task<Boolean> ExecuteForBoolean (HttpRequestMessage request, bool authenticate = true)
// execute and extract JSON payload from response content and convert to RESULT
private static async Task<RESULT> Execute<RESULT>(HttpRequestMessage request, bool authenticate = true)
I can move the unauthorized responses (which my current code isn't handling right now anyway) into a new method CheckResponse that will (for example) log the user out if a 401 is received.