Consuming ASP.NET Core 2.0 Web API Using HttpClient

Problem

How to consume ASP.NET Core Web API using HttpClient.

Solution

We’ll create a library to wrap the functionality of HttpClient. I’ll use builder pattern for this purpose. Add a class with methods for storing the parts of HttpClient.

public class HttpRequestBuilder
{
private HttpMethod method = null;
private string requestUri = "";
private HttpContent content = null;
private string bearerToken = "";
private string acceptHeader = "application/json";
private TimeSpan timeout = new TimeSpan(0, 0, 15);
public HttpRequestBuilder()
{
}
public HttpRequestBuilder AddMethod(HttpMethod method)
{
this.method = method;
return this;
}
public HttpRequestBuilder AddRequestUri(string requestUri)
{
this.requestUri = requestUri;
return this;
}
public HttpRequestBuilder AddContent(HttpContent content)
{
this.content = content;
return this;
}
public HttpRequestBuilder AddBearerToken(string bearerToken)
{
this.bearerToken = bearerToken;
return this;
}
public HttpRequestBuilder AddAcceptHeader(string acceptHeader)
{
this.acceptHeader = acceptHeader;
return this;
}
public HttpRequestBuilder AddTimeout(TimeSpan timeout)
{
this.timeout = timeout;
return this;
}
rest of code

Add a method to send a request using HttpClient and get the response.

public async Task<HttpResponseMessage> SendAsync()
{
// Check required arguments
EnsureArguments();
// Setup request
var request = new HttpRequestMessage
{
Method = this.method,
RequestUri = new Uri(this.requestUri)
};
if (this.content != null)
request.Content = this.content;
if (!string.IsNullOrEmpty(this.bearerToken))
request.Headers.Authorization =
new AuthenticationHeaderValue("Bearer", this.bearerToken);
request.Headers.Accept.Clear();
if (!string.IsNullOrEmpty(this.acceptHeader))
request.Headers.Accept.Add(
new MediaTypeWithQualityHeaderValue(this.acceptHeader));
// Setup client
var client = new System.Net.Http.HttpClient();
client.Timeout = this.timeout;
return await client.SendAsync(request);
}

We’ll also add a factory class to build requests for GET, POST, PUT, PATCH, and DELETE.

public static class HttpRequestFactory
{
public static async Task<HttpResponseMessage> Get(string requestUri)
{
var builder = new HttpRequestBuilder()
.AddMethod(HttpMethod.Get)
.AddRequestUri(requestUri);
return await builder.SendAsync();
}
public static async Task<HttpResponseMessage> Post(
string requestUri, object value)
{
var builder = new HttpRequestBuilder()
.AddMethod(HttpMethod.Post)
.AddRequestUri(requestUri)
.AddContent(new JsonContent(value)) ;
return await builder.SendAsync();
}
public static async Task<HttpResponseMessage> Put(
string requestUri, object value)
{
var builder = new HttpRequestBuilder()
.AddMethod(HttpMethod.Put)
.AddRequestUri(requestUri)
.AddContent(new JsonContent(value));
return await builder.SendAsync();
}
public static async Task<HttpResponseMessage> Patch(
string requestUri, object value)
{
var builder = new HttpRequestBuilder()
.AddMethod(new HttpMethod("PATCH"))
.AddRequestUri(requestUri)
.AddContent(new PatchContent(value));
return await builder.SendAsync();
}
public static async Task<HttpResponseMessage> Delete(string requestUri)
{
var builder = new HttpRequestBuilder()
.AddMethod(HttpMethod.Delete)
.AddRequestUri(requestUri);
return await builder.SendAsync();
}
}

JsonContent, PatchContent, and FileContent are custom classes to simplify the sending of data.

public class JsonContent : StringContent
{
public JsonContent(object value)
: base (JsonConvert.SerializeObject(value), Encoding.UTF8, "application/json")
{
}
public JsonContent(object value, string mediaType)
: base(JsonConvert.SerializeObject(value), Encoding.UTF8, mediaType)
{
}
}
public class PatchContent : StringContent
{
public PatchContent(object value)
: base (JsonConvert.SerializeObject(value), Encoding.UTF8,
"application/json-patch+json")
{
}
}
public class FileContent : MultipartFormDataContent
{
public FileContent(string filePath, string apiParamName)
{
var filestream = File.Open(filePath, FileMode.Open);
var filename = Path.GetFileName(filePath);
Add(new StreamContent(filestream), apiParamName, filename);
}
}

Finally, a few extension methods to help working with HttpResponseMessage class.

public static class HttpResponseExtensions
{
public static T ContentAsType<T>(this HttpResponseMessage response)
{
var data = response.Content.ReadAsStringAsync().Result;
return string.IsNullOrEmpty(data) ?
default(T) :
JsonConvert.DeserializeObject<T>(data);
}
public static string ContentAsJson(this HttpResponseMessage response)
{
var data = response.Content.ReadAsStringAsync().Result;
return JsonConvert.SerializeObject(data);
}
public static string ContentAsString(this HttpResponseMessage response)
{
return response.Content.ReadAsStringAsync().Result;
}
}

We can use the code above like -

private static async Task GetList()
{
var requestUri = $"{baseUri}";
var response = await HttpRequestFactory.Get(requestUri);
Console.WriteLine($"Status: {response.StatusCode}");
var outputModel = response.ContentAsType<List<MovieOutputModel>>();
outputModel.ForEach(item =>
Console.WriteLine("{0} - {1}", item.Id, item.Title));
}

Here is how the sample client looks like.

Note
The sample code has examples of another type of requests too. It uses CRUD API created in a previous post. Download its project and run the API before running this console sample.

Source Code

GitHub

3 Comments

Join the conversation! Your thoughts help the community grow.

Nishanth Kumar7y ago
Excellent, can you please share the post example also and some one help on how to read my urls from applicationsettings.json file
Heino Plaatjies8y ago
Hi, can you share an example to Post and get to api using HttpClient using Windows Forms Applications
Arvind Singh8y ago
Good one.............