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C# HttpClient Example: System.Net.HttpUse the HttpClient type to download a web page. Add System.Net.Http and System.Threading.Tasks.
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HttpClient. Files from the Internet must often be accessed. This requires more time due to reduced locality. During this time, a program can perform other tasks.

Class, notes. The .NET Framework provides a HttpClient class that makes downloading files on separate threads easier. It helps simplify syntax.

To start, we use the async and await keywords. In Main, we start a task and use DownloadPageAsync, an async method, as the target. This method is started—it downloads a web page.

Tip In DownloadPageAsync, we use 3 using-statements. This helps improve system resource usage.

Await We use the await keyword twice. We first call GetAsync and then ReadAsStringAsync. And finally we display the result string.

Using

C# program that uses HttpClient
using System; using System.Net.Http; using System.Threading.Tasks; class Program { static void Main() { Task t = new Task(DownloadPageAsync); t.Start(); Console.WriteLine("Downloading page..."); Console.ReadLine(); } static async void DownloadPageAsync() { // ... Target page. string page = "http://en.wikipedia.org/"; // ... Use HttpClient. using (HttpClient client = new HttpClient()) using (HttpResponseMessage response = await client.GetAsync(page)) using (HttpContent content = response.Content) { // ... Read the string. string result = await content.ReadAsStringAsync(); // ... Display the result. if (result != null && result.Length >= 50) { Console.WriteLine(result.Substring(0, 50) + "..."); } } } }
Downloading page... <!DOCTYPE html> <html lang="en" dir="ltr" class="c...

Static HttpClient. A network connection uses limited system resources. These can become exhausted with the normal "using" pattern on HttpClient.

And A static HttpClient may work better in some programs. If you run out of system resources with HttpClient, try a static HttpClient.

Note The "using" statement should usually be used with types that implement IDisposable. But if this causes an error, it can be omitted.

C# program that uses static HttpClient
using System; using System.Net.Http; using System.Threading.Tasks; class Program { static void Main() { // Run the task. Task.Run(new Action(DownloadPageAsync)); Console.ReadLine(); } static HttpClient _client = new HttpClient(); static async void DownloadPageAsync() { // Use static HttpClient to avoid exhausting system resources for network connections. var result = await _client.GetAsync("http://www.example.com/"); // Write status code. Console.WriteLine("STATUS CODE: " + result.StatusCode); } }
STATUS CODE: OK

A discussion. The functionality of HttpClient overlaps with WebClient. The syntax of these two types is different. WebClient does not currently support the async and await syntax.

Note With WebClient, its "Async" method uses an object token. This is more clumsy.

WebClient

Therefore If async and await are used in the program, the HttpClient is preferable—it gains compiler checking and improved syntax.

A review. HttpClient provides powerful functionality with better syntax support for newer threading features. It supports the await keyword.

Note Thanks to Nedim Ibrahimkadic for the helpful information about reusing a single HttpClient.

HttpClient enables threaded downloads of Internet files with better compiler checking and code validation. It requires newer versions of the .NET Framework.

async

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