I'm creating an app that should import a lis from a Rest Api that connects with an sql server
it is working perfect in postman
but in Xamarin Evrithing comes blank
here is my code
this is the repo
public Alamacenes[] getAlmacenes()
{
try
{
Alamacenes[] almacenes;
var URLWebAPI = "https://www.avila.somee.com/ApiAlexa/api/Almacenes";
using (var Client = new System.Net.Http.HttpClient())
{
var JSON = Client.GetStringAsync(URLWebAPI);
almacenes = JsonConvert.DeserializeObject<Alamacenes[]>(JSON.Result);
}
return almacenes;
}
catch (Exception ex)
{
throw ex;
}
}
this is my codebehind
protected async void OnAppearing()
{
Repositorio repo = new Repositorio();
Alamacenes[] listalmacenes = repo.getAlmacenes();
foreach (var item in listalmacenes)
{
base.OnAppearing();
Almacen.Items.Add(item.CodigoAlmacen.ToString());
Almacen.Items.IndexOf(item.Almacen.ToString());
}
}
and this image is the result
enter image description here
i would like to know if i'm doing something wrong with my code
I think you are setting the list to the picker while is empty, You should await the response and after that set the item source to the picker. Take a look on this quick sample.
//XAML Code
<Picker x:Name="almacenPicker" ItemDisplayBinding="{Binding Almacen}" />
//Code behind code
protected override async void OnAppearing()
{
base.OnAppearing();
var almacenList = await GetAlamacenes();
almacenPicker.ItemsSource = almacenList;
}
public Task<List<Almacene>> GetAlamacenes()
{
return GetAsync<List<Almacene>>("https://www.avila.somee.com/ApiAlexa/api/Almacenes");
}
public async Task<TResult> GetAsync<TResult>(string uri)
{
var httpClient = new HttpClient();
HttpResponseMessage response = await httpClient.GetAsync(uri);
var content = await response.Content.ReadAsStringAsync();
return await Task.Run(() => JsonConvert.DeserializeObject<TResult>(content));
}
Related
I want to connect to my Web api with these code
but when debugger arrived on
var response = await client.GetAsync(url);
skip without any error,
UPDATE
it's mean:
I set breakpoint and when debugger arrive on that line after that don't catch the next line and exit from this block and jump to caller method
public class Constants
{
public const string BaseUrl = "https://localhost:44301/";
}
2:
public static class GeneralUrl
{
public static string ComapnyNameUrl()
{
return string.Format(Constants.BaseUrl);
}
}
3: change to 3.1
public async static Task<List<CompanyName>> GetCompanyNamesAsync()
{
List<CompanyName> companyNameList = new List<CompanyName>();
string url = GeneralUrl.ComapnyNameUrl() + "api/CompanyName";
using (HttpClient client = new HttpClient())
{
var response = await client.GetAsync(url);
if (response.IsSuccessStatusCode)
{
string content =await response.Content.ReadAsStringAsync();
companyNameList = JsonConvert.DeserializeObject<List<CompanyName>>(content);
}
}
return companyNameList;
}
UPDATE 2
3.1:
I change above code to this but the problen exist
Update
public class CompanyNameService
{
private static HttpClient client = new HttpClient();
public async static Task<List<CompanyName>> GetCompanyNamesAsync()
{
List<CompanyName> companyNameList = new List<CompanyName>();
string url = GeneralUrl.ComapnyNameUrl() + "api/Companyname";
var response = await client.GetAsync(url);
if (response.IsSuccessStatusCode)
{
string content =await response.Content.ReadAsStringAsync();
companyNameList = JsonConvert.DeserializeObject<List<CompanyName>>(content);
}
return companyNameList;
}
}
also my startup.cs in my web api is
services.AddControllers().AddJsonOptions(o =>
{
o.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.Preserve;
o.JsonSerializerOptions.MaxDepth = 0;
});
services.AddControllers().AddNewtonsoftJson(options =>
options.SerializerSettings.ReferenceLoopHandling =
Newtonsoft.Json.ReferenceLoopHandling.Ignore);
END OF UPDATE 2
and final for calling them is=>
4:
protected override async void OnAppearing()
{
base.OnAppearing();
var companyName = await CompanyNameService.GetCompanyNamesAsync();
}
I think that it was for async method what is my mistake??
UPDATE
In debug mode in output windows I have this message
02-10 13:04:21.568 I/Choreographer( 790): Skipped 428 frames! The application may be doing too much work on its main thread.
02-10 13:04:21.642 I/OpenGLRenderer( 790): Davey! duration=7213ms; Flags=0, IntendedVsync=51372290598463, Vsync=51379423931511, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=51379430268200, AnimationStart=51379430347200, PerformTraversalsStart=51379430673700, DrawStart=51379441519600, SyncQueued=51379446948700, SyncStart=51379447122900, IssueDrawCommandsStart=51379447270300, SwapBuffers=51379483411800, FrameCompleted=51379504170100, DequeueBufferDuration=409000, QueueBufferDuration=612000,
UPDATE 3:
As I try use local address, after more than 5 min got a message in out put window that "the operation in canceled" and catch the exception with the same message.
Try this:
protected async override void OnAppearing()
{
base.OnAppearing();
var companyName = await GetCompanyNamesAsync();
}
public async static Task<List<CompanyName>> GetCompanyNamesAsync()
{
List<CompanyName> companyNameList = new List<CompanyName>();
string url = GeneralUrl.ComapnyNameUrl() + "api/Companyname";
using (HttpClient client = new HttpClient())
{
var response = await client.GetStringAsync(url);
companyNameList = JsonConvert.DeserializeObject<List<CompanyName>>(response);
}
return companyNameList;
}
I have my Web Api on a production server online and working well in postman and in Xamarin forms so far until I needed to do a Get Request and does not return any data. Infact it stops at the GetAsStringAsync line and does not continue. Instead, it jumps out of the method and then nothing more.
Does any one know what the problem could be? I have checked and made sure my Internet is working and the Uri too.
This is where I am doing my Get in Xamarin forms:
public async Task<List<OfferModel>> AllOffers()
{
var httpclient = new HttpClient();
httpclient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", Settings.AccessToken);
//it does not continue after this line, it jumps out of the method instead
var response = await httpclient.GetStringAsync(UrlConstants.offerurl);
var data =JsonConvert.DeserializeObject<List<OfferModel(response);
return data;
}
Solution 1
Can you try access task via awaiter it may be wait until result when responded
public class HttpHelperService
{
public async Task<List<OfferModel>> AllOffers()
{
List<OfferModel> result;
string responseBody;
using (HttpClient client = new HttpClient())
{
try
{
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", Settings.AccessToken);
HttpResponseMessage response = client.GetStringAsync(new Uri(UrlConstants.offerurl)).GetAwaiter().GetResult();
result = JsonConvert.DeserializeObject<List<OfferModel>>(response);
}
catch (Exception ex)
{
result = null;
}
return result;
}
}
}
Solution 2
public class MyPage : ContentPage
{
//Here is your page constructor
public MyPage()
{
GetServices(); //--> call here without awaiter
}
}
//Here is your awaiter method
private async void GetServices()
{
LoadingPopupService.Show();
var result = await HttpService.AllOffers();
LoadingPopupService.Hide();
}
//Here is your service.
public async Task<List<OfferModel>> AllOffers()
{
var httpclient = new HttpClient();
httpclient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", Settings.AccessToken);
var response = await httpclient.GetStringAsync(UrlConstants.offerurl);
var data =JsonConvert.DeserializeObject<List<OfferModel(response);
return data;
}
Using the Template Studio extension for Visual Studio, I generated a project solution base and am now attempting to interject the app load process with a HTTP request before proceeding the render the page view.
App.xaml.cs
using System;
using Braytech_3.Services;
using Windows.ApplicationModel.Activation;
using Windows.Storage;
using Windows.UI.Xaml;
namespace Braytech_3
{
public sealed partial class App : Application
{
private Lazy<ActivationService> _activationService;
private ActivationService ActivationService
{
get { return _activationService.Value; }
}
public App()
{
InitializeComponent();
APIRequest();
// Deferred execution until used. Check https://msdn.microsoft.com/library/dd642331(v=vs.110).aspx for further info on Lazy<T> class.
_activationService = new Lazy<ActivationService>(CreateActivationService);
}
protected override async void OnLaunched(LaunchActivatedEventArgs args)
{
if (!args.PrelaunchActivated)
{
await ActivationService.ActivateAsync(args);
}
}
protected override async void OnActivated(IActivatedEventArgs args)
{
await ActivationService.ActivateAsync(args);
}
private async void APIRequest()
{
//Create an HTTP client object
Windows.Web.Http.HttpClient httpClient = new Windows.Web.Http.HttpClient();
//Add a user-agent header to the GET request.
var headers = httpClient.DefaultRequestHeaders;
Uri requestUri = new Uri("https://json_url");
//Send the GET request asynchronously and retrieve the response as a string.
Windows.Web.Http.HttpResponseMessage httpResponse = new Windows.Web.Http.HttpResponseMessage();
string httpResponseBody = "";
try
{
//Send the GET request
httpResponse = await httpClient.GetAsync(requestUri);
httpResponse.EnsureSuccessStatusCode();
httpResponseBody = await httpResponse.Content.ReadAsStringAsync();
APITempSave(httpResponseBody);
}
catch (Exception ex)
{
}
}
private async void APITempSave(string json)
{
StorageFolder tempFolder = ApplicationData.Current.TemporaryFolder;
if (await tempFolder.TryGetItemAsync("APIData.json") != null)
{
StorageFile APIData = await tempFolder.GetFileAsync("APIData.json");
await FileIO.WriteTextAsync(APIData, json);
}
else
{
StorageFile APIData = await tempFolder.CreateFileAsync("APIData.json");
await FileIO.WriteTextAsync(APIData, json);
}
}
private ActivationService CreateActivationService()
{
return new ActivationService(this, typeof(Views.VendorsPage), new Lazy<UIElement>(CreateShell));
}
private UIElement CreateShell()
{
return new Views.ShellPage();
}
}
}
I think what I need to do is call _activationService = new Lazy<ActivationService>(CreateActivationService); once APITempSave() has been called but I am unsure of how to do so and what best practices are.
Any guidance would be greatly appreciated!
After further investigation and familiarisation with the generated solution, as well as additional Googling of await, async, and Tasks<>, I was able to implement the request as a service alongside items such as ThemeSelector, and ToastNotifications.
The ThemeSelector is one of the first things to be called in order to determine light and dark theme mode for the current user, so I was able to model my service around it and call it at the same time.
This is obviously very specific to the code that template studio generates, but some concepts are shared and should anyone else look for similar answers in the future maybe they'll find this.
APIRequest.cs (Service)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.Storage;
namespace Braytech_3.Services
{
public static class APIRequest
{
internal static async Task Request()
{
//Create an HTTP client object
Windows.Web.Http.HttpClient httpClient = new Windows.Web.Http.HttpClient();
//Add a user-agent header to the GET request.
var headers = httpClient.DefaultRequestHeaders;
Uri requestUri = new Uri("https://json_url");
//Send the GET request asynchronously and retrieve the response as a string.
Windows.Web.Http.HttpResponseMessage httpResponse = new Windows.Web.Http.HttpResponseMessage();
string httpResponseBody = "";
try
{
//Send the GET request
httpResponse = await httpClient.GetAsync(requestUri);
httpResponse.EnsureSuccessStatusCode();
httpResponseBody = await httpResponse.Content.ReadAsStringAsync();
await APITempSave(httpResponseBody);
}
catch (Exception ex)
{
}
}
internal static async Task APITempSave(string json)
{
StorageFolder tempFolder = ApplicationData.Current.TemporaryFolder;
if (await tempFolder.TryGetItemAsync("APIData.json") != null)
{
StorageFile APIData = await tempFolder.GetFileAsync("APIData.json");
await FileIO.WriteTextAsync(APIData, json);
}
else
{
StorageFile APIData = await tempFolder.CreateFileAsync("APIData.json");
await FileIO.WriteTextAsync(APIData, json);
}
}
}
}
ActiviationService.cs (originally called by App.xaml.cs)
private async Task InitializeAsync()
{
await ThemeSelectorService.InitializeAsync();
await APIRequest.Request();
}
i am trying to make an asynchronous call to a webservice.
I would like to make this call when opening the app (App.xaml.cs).
According to the answer that comes back to me, it has to navigate to a particular page
But I do not work.
public partial class App : PrismApplication
{
public App(IPlatformInitializer initializer = null) : base(initializer) { }
protected override void OnInitialized()
{
InitializeComponent();
try
{
CheckLogin().Wait();
}
catch (Exception e)
{
var t = e;
}
}
private static async Task CheckLogin()
{
try
{
var login = new Login
{
Email = "test#test.com",
Password = "test",
};
var client = new HttpClient { BaseAddress = new Uri("http://www.api.com/test/") };
var data = JsonConvert.SerializeObject(login);
var content = new StringContent(data, Encoding.UTF8, "application/json");
var response = await client.PostAsync(#"api/it-IT/auth/token", content); //crash without error, freeze
if (response.IsSuccessStatusCode)
{
var successResult = JsonConvert.DeserializeObject<HttpResponseMessage>(response.Content.ReadAsStringAsync().Result);
if (successResult != null)
{
//return true;
}
else
{
//return false;
}
}
}
catch (Exception e)
{
var t = e;
}
}
protected override void RegisterTypes()
{
Container.RegisterTypeForNavigation<NavigationPage>();
Container.RegisterTypeForNavigation<MainPage>();
Container.RegisterTypeForNavigation<MainPage2>();
Container.RegisterTypeForNavigation<MainPage3>();
}
}
When does the postasync call does not go more forward, not I get no errors, but does not proceed.
But if I try the same code in an application console, everything works fine, why?
class Program
{
static void Main(string[] args)
{
Console.WriteLine("A");
CheckLogin().Wait();
Console.WriteLine("K");
Console.ReadKey();
}
private static async Task CheckLogin()
{
try
{
var login = new Login
{
Email = "test#test.com",
Password = "#test",
};
var client = new HttpClient { BaseAddress = new Uri("http://www.api.com/test/") };
var data = JsonConvert.SerializeObject(login);
var content = new StringContent(data, Encoding.UTF8, "application/json");
var response = await client.PostAsync(#"api/it-IT/auth/token", content);
if (response.IsSuccessStatusCode)
{
}
}
catch (Exception e)
{
var t = e;
}
}
}
If I try to do the same operation within a command with wait I do not work the same error, but if I do await, it will work fine, but in App.xaml.cs in OnInitialized() I can not put await
public DelegateCommand callCommand { get; set; }
public MainPage2ViewModel()
{
callCommand = new DelegateCommand(Call);
}
private void Call()
{
//await CheckLogin(); // work
CheckLogin().Wait(); // not work the same problem
var i = "pippo";
}
private async Task CheckLogin()
{
....
}
Is there anything to set with xamarin or with prism?
I've also the same strange error...
i fix with this workaround (use an async void that wrap async task)...
public App()
{
InitializeComponent();
Current.MainPage = new LoadingPage();
}
protected override void OnStart()
{
MagicInit();
base.OnStart();
}
public static async void MagicInit()
{
var f = await FileSystem.Current.LocalStorage.CreateFileAsync("db.sqlite", CreationCollisionOption.OpenIfExists);
DbConnection = f.Path;
await DataService.DbFill();
User = await DataService.Instance.Table<SpUser>().FirstOrDefaultAsync();
Current.MainPage = User != null ? (Page)new MainPage() : new LoginPage();
}
First of all, I would like to say, I'm quite new to C#.
I'm trying to create a POST request which sends some data to a PHP file somewhere on a different server.
Now, after the request is send I would like to see the response, as I'm sending back a JSON string from the server as a success message.
When I use the following code:
public MainPage()
{
this.InitializeComponent();
Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().SetDesiredBoundsMode(Windows.UI.ViewManagement.ApplicationViewBoundsMode.UseCoreWindow);
responseBlockTxt.Text = start();
}
public string start()
{
var response = sendRequest();
System.Diagnostics.Debug.WriteLine(response);
return "";
}
public async Task<string> sendRequest()
{
using (var client = new HttpClient())
{
var values = new Dictionary<string, string>
{
{ "vote", "true" },
{ "slug", "the-slug" }
};
var content = new FormUrlEncodedContent(values);
var response = await client.PostAsync("URL/api.php", content);
var responseString = await response.Content.ReadAsStringAsync();
return responseString;
}
}
The output is:
System.Threading.Tasks.Task`1[System.String]
So, how would I see all the results from this?
Go Async all the way. Avoid blocking calls when calling async methods. async void is allowed in event handlers so update page to perform the call on load event
Read up on Async/Await - Best Practices in Asynchronous Programming
And then update your code accordingly
public MainPage() {
this.InitializeComponent();
Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().SetDesiredBoundsMode(Windows.UI.ViewManagement.ApplicationViewBoundsMode.UseCoreWindow);
this.Loaded += OnLoaded;
}
public async void OnLoaded(object sender, RoutedEventArgs e) {
responseBlockTxt.Text = await start();
}
public async Task<string> start() {
var response = await sendRequest();
System.Diagnostics.Debug.WriteLine(response);
return response;
}
private static HttpClient client = new HttpClient();
public async Task<string> sendRequest() {
var values = new Dictionary<string, string> {
{ "vote", "true" },
{ "slug", "the-slug" }
};
var content = new FormUrlEncodedContent(values);
using(var response = await client.PostAsync("URL/api.php", content)) {
var responseString = await response.Content.ReadAsStringAsync();
return responseString;
}
}
I Guess
public string start()
{
var response = sendRequest();
Task<String> t = sendRequest();
System.Diagnostics.Debug.WriteLine(t.Result);
return "";
}
public async Task<string> sendRequest()
{
using (var client = new HttpClient())
{
var values = new Dictionary<string, string>
{
{ "vote", "true" },
{ "slug", "the-slug" }
};
var content = new FormUrlEncodedContent(values);
var response = await client.PostAsync("URL/api.php", content);
var responseString = await response.Content.ReadAsStringAsync();
return responseString;
}
}
The problem is in the start method, the SendRequest method returns a Task<string> and that's what you get on your response variable. Since you are attempting to run an async method synchronously you have to do some extra stuff, try this:
public string start()
{
var response = sendRequest().ConfigureAwait(true)
.GetAwaiter()
.GetResult();
System.Diagnostics.Debug.WriteLine(response);
return "";
}
That get the actual result inside your awaitable Task<string>. If you want to find some more info on this take a look at this question
public string start()
{
var response = sendRequest().ConfigureAwait(true)
.GetAwaiter()
.GetResult();
System.Diagnostics.Debug.WriteLine(response);
return "";
}
I have Tried this. It is working perfectly.