HttpClient Extension Methods

In its HttpClient class and extension methods (from the Microsoft.AspNet.WebApi.Client), Microsoft has created some simple and powerful methods for sending HTTP requests and handling the responses. For many scenarios, the Microsoft-provided methods may be sufficient. EDennis.AspNetCore.Base adds some HttpClient extension methods to facilitate forwarding requests from a parent HTTP request and to facilitate creating return values that include the status code and an optional response body.

StatusCodeResult and HttpClientResult

The current extension methods return either a Microsoft.AspNetCore.Mvc.StatusCodeResult or an EDennis.AspNetCore.Base.Web.HttpClientResult. The StatusCodeResult type is the regular Microsoft StatusCodeResult that can be cast to an int. The HttpClientResult type is a typed analog of Microsoft's ObjectResult, which includes both the response body and the status code. The HttpClientResult type has some properties and methods that make it easy to extract the desired data or to translate to an ObjectResult or StatusCodeResult.

HttpClientResult

Type Parameters Properties

HttpClientResult has one type parameter:

Type Parameter	Constraints
T	T is any primitive or class type, including a generic collection type

Properties

Property	Description
public int StatusCode { get; set; }	This is the HTTP response status code
public T Value { get; set; }	This is the deserialized response body

Methods

Method	Description
public ObjectResult ObjectResult()	Transforms the result into a Microsoft.AspNetCore.Mvc.ObjectResult
public T Value { get; set; }	Transforms the result into Microsoft.AspNetCore.Mvc.StatusCodeResult

HttpClient Extension Methods (From This Library)

What follows are descriptions and sample code for each of the extension methods. Below each example is the equivalent code required to produce the desired response-body/status-code return object.

Get and GetAsync

This library provides a generic Get method, which bundles up the response body and status code into an HttpClientResult.

Example

public HttpClientResult<IEnumerable<Color>> GetAll() {
    return HttpClient.Get<IEnumerable<Color>>(CONTROLLER_PATH);
}

Equivalent Example Using Microsoft Methods

public HttpClientResult<IEnumerable<Color>> GetAll_Microsoft() {
    var result = HttpClient.GetAsync(CONTROLLER_PATH).Result;
    var content = result.Content.ReadAsAsync<IEnumerable<Color>>().Result;
    return new HttpClientResult<IEnumerable<Color>> {
        StatusCode = (int)result.StatusCode,
        Value = content
    };
}

Post and PostAsync

This library provides a generic Post method, which bundles up the response body and status code into an HttpClientResult. Importantly, this response type gives the endpoints the option of returning a status code, a response body, or a response body and status code.

Example

public HttpClientResult<Color> Post(Color color) {
    return HttpClient.Post(CONTROLLER_PATH, color);
}

Equivalent Example Using Microsoft Methods

//requires Microsoft.AspNet.WebApi.Client NuGet package
public HttpClientResult<Color> Post_Microsoft(Color color) {
    var result = HttpClient.PostAsJsonAsync(CONTROLLER_PATH, color).Result;
    var content = result.Content.ReadAsAsync<Color>().Result;
    return new HttpClientResult<Color> {
        StatusCode = (int)result.StatusCode,
        Value = content
    };
}

Put and PutAsync

This library provides a generic Put method, which bundles up the response body and status code into an HttpClientResult. Again, this response type gives the endpoints the option of returning a status code, a response body, or a response body and status code.

Example

public HttpClientResult<Color> Put(Color color, string name) {
    return HttpClient.Put($"{CONTROLLER_PATH}/{name}", color);
}

Equivalent Example Using Microsoft Methods

//requires Microsoft.AspNet.WebApi.Client NuGet package
public HttpClientResult<Color> Put_Microsoft(Color color, string name) {
    var result = HttpClient.PutAsJsonAsync($"{CONTROLLER_PATH}/{name}", color).Result;
    var content = result.Content.ReadAsAsync<Color>().Result;
    return new HttpClientResult<Color> {
        StatusCode = (int)result.StatusCode,
        Value = content
    };
}

Delete and DeleteAsync

This library provides a generic Delete method, which returns a simple StatusCodeResult. (For this particular method, the type parameter is only used to differentiate the method from the Microsoft method with the same signature.)

Example

public StatusCodeResult Delete(string name) {
    return HttpClient.Delete<Color>($"{CONTROLLER_PATH}/{name}");
}

Equivalent Example Using Microsoft Methods

public StatusCodeResult Delete_Microsoft(string name) {
    var result = HttpClient.DeleteAsync($"{CONTROLLER_PATH}/{name}").Result;
    var content = result.Content.ReadAsAsync<Color>().Result;
    return new StatusCodeResult((int)result.StatusCode);
}

Forward

Sometimes, a developer needs to forward a parent HTTP request to a child API. For example, the developer may be using an application development framework that generates views that are designed to communicate directly with controllers that are designed to work directly with Linq, Entity Framework, or some other object-relational mapping software. Unfortunately, if the developer wants to insert a microservices layer between the user interface and controllers, then the developer may have some significant coding work to stitch everything together.

The current library provides a typed Forward method that takes the parent HttpRequest as a parameter; copies the request method, request body, query parameters, and relevant headers (and cookies) to a HttpRequestMessage; sends the HttpRequestMessage to some designated endpoint, and returns an HttpClientResult object. Note that there is no asynchronous version of this method because the method relies upon access to the parent HttpRequest, which could exceed its lifetime before an asynchronous method had executed.

Example

public HttpClientResult<Color> Get_Forward(HttpRequest request) {
    return HttpClient.Forward<Color>(request, CONTROLLER_PATH);
}

Equivalent Example Using Microsoft Methods

(There is no easy way to implement request forwarding with the Microsoft methods or extension methods. To see how the library implements Forward, look at the following methods from the HttpClientExtensions class:

• private static HttpClientResult<T> ForwardRequest<T>(this HttpClient client, HttpRequestMessage msg, string relativeUrlFromBase)
• private static HttpRequestMessage ToHttpRequestMessage(this HttpRequest httpRequest, HttpClient client)
• private static HttpRequestMessage ToHttpRequestMessage<T>(this HttpRequest httpRequest, HttpClient client, T body)
• private static HttpRequestMessage CopyMethod(this HttpRequestMessage msg, HttpRequest req)
• private static HttpRequestMessage CopyHeaders(this HttpRequestMessage msg, HttpRequest req, HttpClient client)
• private static HttpRequestMessage CopyQueryString(this HttpRequestMessage msg, HttpRequest req)
• private static HttpRequestMessage CopyCookies(this HttpRequestMessage msg, HttpRequest req)
• private static HttpRequestMessage CopyContent(this HttpRequestMessage msg, HttpRequest req)

Other Extension Methods

This library includes a few miscellaneous extension methods for HttpClient:

Method	Description
SendReset and SendResetAsync	Cleans up the TestDbContextCache after execution of tests
Ping and PingAsync	Checks to see if the HttpClient's target server is available (using only TCP)