C# Online Compiler | .NET Fiddle

using System;
using System.Net.Http;
using System.Threading.Tasks;

namespace HttpclientTestapp
{
	class Program
	{
		/// <summary>
		/// static_client
		/// </summary>
		private static readonly HttpClient static_client = new HttpClient();
		/// <summary>
		/// TEST_URL
		/// </summary>
		private static readonly string TEST_URL = "https://www.yicai.com";
		/// <summary>
		/// HttpClient test main
		/// </summary>
		/// <see cref = "https :  / / docs . microsoft . com / zh - cn / dotnet / api / system . net . http . httpclient ? view  =  netcore - 2 . 2"/>
		/// <param name = "args">args</param>
		/// <returns></returns>
		public static async Task Main(string[] args)
		{
			Console.WriteLine("Starting connections");
			for (int i = 0; i < 20; i++)
			{
				await StaticClientWay();
			}

			Console.WriteLine("Connections done");
			Console.ReadLine();
		}

		private static async Task RequestByUsing()
		{
			using (var client = new HttpClient())
			{
				var result = await client.GetAsync(TEST_URL);
				Console.WriteLine(result.StatusCode);
			}
		}

		private static async Task WrongMethod()
		{
			var client = new HttpClient();
			var result = await client.GetAsync(TEST_URL);
			Console.WriteLine(result.StatusCode);
		}

		private static async Task StaticClientWay()
		{
			var result = await static_client.GetAsync(TEST_URL);
			Console.WriteLine(result.StatusCode);
		}
	}
}

 
using System;
using System.Net.Http;
using System.Threading.Tasks;
​
namespace HttpclientTestapp
{
    class Program
    {
        /// <summary>
        /// static_client
        /// </summary>
        private static readonly HttpClient static_client = new HttpClient();
        /// <summary>
        /// TEST_URL
        /// </summary>
        private static readonly string TEST_URL = "https://www.yicai.com";
        /// <summary>
        /// HttpClient test main
        /// </summary>
        /// <see cref = "https :  / / docs . microsoft . com / zh - cn / dotnet / api / system . net . http . httpclient ? view  =  netcore - 2 . 2"/>
        /// <param name = "args">args</param>
        /// <returns></returns>
        public static async Task Main(string[] args)
        {

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