Starting work on HttpClientFactory documentation

aspnetcore/fundamentals/http-requests/samples/Controllers/ThirdPartyController.cs

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+using System;
+using System.Net;
+using Microsoft.AspNetCore.Mvc;
+
+namespace HttpClientFactorySample.Controllers
+{
+    public class ThirdPartyController : Controller
+    {
+        [Route("unreliable")]
+        public IActionResult UnreliableEndpoint()
+        {
+            var second = DateTime.UtcNow.Second;
+
+            // about 50% of the time this will fail
+            return second % 2 != 0 ? Ok() : StatusCode(HttpStatusCode.ServiceUnavailable);
+        }
+    }
+}

aspnetcore/fundamentals/http-requests/samples/Controllers/UnreliableConsumerController.cs

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+using System;
+using System.Threading.Tasks;
+using HttpClientFactorySample.Services;
+using Microsoft.AspNetCore.Mvc;
+
+namespace HttpClientFactorySample.Controllers
+{
+    public class UnreliableConsumerController : Controller
+    {
+        private readonly UnreliableEndpointCallerService _unreliableEndpointCallerService;
+
+        public UnreliableConsumerController(UnreliableEndpointCallerService unreliableEndpointCallerService)
+        {
+            _unreliableEndpointCallerService = unreliableEndpointCallerService;
+        }
+
+        [Route("unreliable-consumer")]
+        public async Task<IActionResult> UnreliableEndpointConsumer()
+        {
+            // Builds a URI to what we will imagine is an external endpoint that is unreliable. For this sample we are hosting our own unreliable endpoint to demonstrate!
+
+            var url = Url.Action("UnreliableEndpoint", "ThirdParty");
+
+            var uriBuilder = new UriBuilder
+            {
+                Scheme = HttpContext.Request.Scheme,
+                Host = HttpContext.Request.Host.Host,
+                Port = HttpContext.Request.Host.Port ?? 80,
+                Path = url
+            };
+
+            // call the typed client that has been registered in ConfigureServices
+
+            var status = await _unreliableEndpointCallerService.GetDataFromUnreliableEndpoint(uriBuilder.Uri.ToString());
+
+            return Ok(status);
+        }
+    }
+}

aspnetcore/fundamentals/http-requests/samples/GitHub/GitHubBranch.cs

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+namespace HttpClientFactorySample.GitHub
+{
+    /// <summary>
+    /// A partial representation of a branch object from the GitHub API
+    /// </summary>
+    public class GitHubBranch
+    {
+        public string Name { get; set; }
+    }
+}

aspnetcore/fundamentals/http-requests/samples/GitHub/GitHubIssue.cs

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+using System;
+using Newtonsoft.Json;
+
+namespace HttpClientFactorySample.GitHub
+{
+    /// <summary>
+    /// A partial representation of an issue object from the GitHub API
+    /// </summary>
+    public class GitHubIssue
+    {
+        [JsonProperty(PropertyName = "html_url")]
+        public string Url { get; set; }
+
+        public string Title { get; set; }
+
+        [JsonProperty(PropertyName = "created_at")]
+        public DateTime Created { get; set; }
+    }
+}

aspnetcore/fundamentals/http-requests/samples/GitHub/GitHubPullRequest.cs

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+namespace HttpClientFactorySample.GitHub
+{
+    /// <summary>
+    /// A partial representation of a pull request object from the GitHub API
+    /// </summary>
+    public class GitHubPullRequest
+    {
+        public string Title { get; set; }
+    }
+}

aspnetcore/fundamentals/http-requests/samples/GitHub/GitHubService.cs

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+using System;
+using System.IO;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+
+namespace HttpClientFactorySample.GitHub
+{
+    /// <summary>
+    /// Exposes methods to return GitHub API data
+    /// </summary>
+    #region snippet1
+    public class GitHubService
+    {
+        public HttpClient Client { get; }
+
+        public GitHubService(HttpClient client)
+        {
+            client.BaseAddress = new Uri("https://api.github.com/");
+            client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json"); // GitHub API versioning
+            client.DefaultRequestHeaders.Add("User-Agent", "HttpClientFactory-Sample"); // GitHub requires a user-agent
+
+            Client = client;
+        }
+
+        public async Task<GitHubIssue> GetLatestDocsIssue()
+        {
+            var response = await Client.GetAsync("/repos/aspnet/docs/issues?state=open&sort=created&direction=desc", HttpCompletionOption.ResponseHeadersRead);
+
+            response.EnsureSuccessStatusCode();
+
+            using (var stream = await response.Content.ReadAsStreamAsync())
+            using (var streamReader = new StreamReader(stream))
+            using (var jsonReader = new JsonTextReader(streamReader))
+            {
+                var serializer = new JsonSerializer();
+
+                while (await jsonReader.ReadAsync())
+                {
+                    if (jsonReader.TokenType == JsonToken.StartObject)
+                    {
+                        var issue = serializer.Deserialize<GitHubIssue>(jsonReader);
+
+                        if (issue != null)
+                        {
+                            return issue; // we only want the first object
+                        }
+                    }
+                }
+            }
+
+            return null;
+        }
+    }
+    #endregion
+}

aspnetcore/fundamentals/http-requests/samples/GitHub/RepoService.cs

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+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+
+namespace HttpClientFactorySample.GitHub
+{
+    #region snippet1
+    public class RepoService
+    {
+        private readonly HttpClient _httpClient; // not exposed publically
+
+        public RepoService(HttpClient client)
+        {
+            _httpClient = client;
+        }
+
+        public async Task<IEnumerable<string>> GetRepos()
+        {
+            var response = await _httpClient.GetAsync("aspnet/repos");
+
+            response.EnsureSuccessStatusCode();
+
+            var responseContent = await response.Content.ReadAsStringAsync();
+
+            return JsonConvert.DeserializeObject<IEnumerable<string>>(responseContent);
+        }
+    }
+    #endregion
+}

aspnetcore/fundamentals/http-requests/samples/Handlers/RequestDataHandler.cs

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+using System;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+
+namespace HttpClientFactorySample.Handlers
+{
+    #region snippet1
+    public class RequestDataHandler : DelegatingHandler
+    {
+        private readonly ILogger<RequestDataHandler> _logger;
+
+        private const string RequestSourceHeaderName = "Request-Source";
+        private const string RequestSource = "HttpClientFactorySampleApp";
+        private const string RequestIdHeaderName = "Request-Identifier";
+
+        public RequestDataHandler(ILogger<RequestDataHandler> logger)
+        {
+            _logger = logger;
+        }
+
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, 
+            CancellationToken cancellationToken)
+        {
+            var identifier = Guid.NewGuid(); // some information we want to generate and add per request
+
+            _logger.LogInformation($"Starting request {identifier}");
+
+            request.Headers.Add(RequestSourceHeaderName, RequestSource);
+            request.Headers.Add(RequestIdHeaderName, identifier.ToString());
+
+            return base.SendAsync(request, cancellationToken);
+        }
+    }
+    #endregion
+}

aspnetcore/fundamentals/http-requests/samples/Handlers/SecureRequestHandler.cs

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+using System;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace HttpClientFactorySample.Handlers
+{
+    public class SecureRequestHandler : DelegatingHandler
+    {
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
+            CancellationToken cancellationToken)
+        {
+            if (request.RequestUri.Scheme == Uri.UriSchemeHttp)
+            {
+                var builder = new UriBuilder(request.RequestUri) { Scheme = Uri.UriSchemeHttps };
+                request.RequestUri = builder.Uri;
+            }
+
+            return base.SendAsync(request, cancellationToken);
+        }
+    }
+}

aspnetcore/fundamentals/http-requests/samples/Handlers/ValidateHeaderHandler.cs

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+using System.Net;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace HttpClientFactorySample.Handlers
+{
+    #region snippet1
+    public class ValidateHeaderHandler : DelegatingHandler
+    {
+        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
+            CancellationToken cancellationToken)
+        {
+            if (!request.Headers.Contains("X-API-KEY"))
+            {
+                return new HttpResponseMessage(HttpStatusCode.BadRequest)
+                {
+                    Content = new StringContent("You must supply an API key header called X-API-KEY")
+                };
+            }
+
+            return await base.SendAsync(request, cancellationToken);
+        }
+    }
+    #endregion
+}

aspnetcore/fundamentals/http-requests/samples/HttpClientFactorySample.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.0-preview2-final" />
+    <PackageReference Include="Microsoft.Extensions.Http.Polly" Version="2.1.0-preview2-final" />
+    <PackageReference Include="Microsoft.VisualStudio.Web.BrowserLink" Version="2.1.0-preview2-final" />
+    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.1.0-preview2-final" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.1.0-preview1-final" />
+  </ItemGroup>
+
+</Project>

aspnetcore/fundamentals/http-requests/samples/Pages/BasicUsage.cshtml

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+@page
+@model BasicUsageModel
+@{
+}
+
+<h1>Branches for Docs Repo</h1>
+
+<ul>
+    @foreach (var branch in Model.Branches)
+    {
+        <li>@branch.Name</li>
+    }
+</ul>

aspnetcore/fundamentals/http-requests/samples/Pages/BasicUsage.cshtml.cs

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+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading.Tasks;
+using HttpClientFactorySample.GitHub;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Newtonsoft.Json;
+
+namespace HttpClientFactorySample.Pages
+{
+    #region snippet1
+    public class BasicUsageModel : PageModel
+    {
+        private readonly IHttpClientFactory _clientFactory;
+
+        public IEnumerable<GitHubBranch> Branches { get; private set; }
+
+        public BasicUsageModel(IHttpClientFactory clientFactory)
+        {
+            _clientFactory = clientFactory;
+        }
+
+        public async Task OnGet()
+        {
+            var request = new HttpRequestMessage(HttpMethod.Get, "https://api.github.com/repos/aspnet/docs/branches" );
+            request.Headers.Add("Accept", "application/vnd.github.v3+json");
+            request.Headers.Add("User-Agent", "HttpClientFactory-Sample");
+
+            var client = _clientFactory.CreateClient();
+
+            var response = await client.SendAsync(request);
+
+            if (response.IsSuccessStatusCode)
+            {
+                var data = await response.Content.ReadAsStringAsync();
+                Branches = JsonConvert.DeserializeObject<IEnumerable<GitHubBranch>>(data);
+            }
+            else
+            {
+                Branches = Array.Empty<GitHubBranch>();
+            }
+        }
+    }
+    #endregion
+}

aspnetcore/fundamentals/http-requests/samples/Pages/Error.cshtml

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+@page
+@model ErrorModel
+@{
+    ViewData["Title"] = "Error";
+}
+
+<h1 class="text-danger">Error.</h1>
+<h2 class="text-danger">An error occurred while processing your request.</h2>
+
+@if (Model.ShowRequestId)
+{
+    <p>
+        <strong>Request ID:</strong> <code>@Model.RequestId</code>
+    </p>
+}
+
+<h3>Development Mode</h3>
+<p>
+    Swapping to <strong>Development</strong> environment will display more detailed information about the error that occurred.
+</p>
+<p>
+    <strong>Development environment should not be enabled in deployed applications</strong>, as it can result in sensitive information from exceptions being displayed to end users. For local debugging, development environment can be enabled by setting the <strong>ASPNETCORE_ENVIRONMENT</strong> environment variable to <strong>Development</strong>, and restarting the application.
+</p>