使用c#获取html变量

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

class Program
{
    static async Task Main(string[] args)
    {
        using (HttpClient client = new HttpClient())
        {
            var formContent = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("username", "value")
            });

            var response = await client.PostAsync("https://example.com/page", formContent);
            var responseContent = await response.Content.ReadAsStringAsync();

            // 处理HTML页面的响应内容
            Console.WriteLine(responseContent);
        }
    }
}