.NET客户端应用程序:如果代理服务器如何访问Web服务？

using System;
using System.Net;

class Program
{
    static void Main()
    {
        WebClient client = new WebClient();
        string url = "http://example.com/webservice";
        string result = client.DownloadString(url);
        Console.WriteLine(result);
    }
}

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

class Program
{
    static async Task Main()
    {
        HttpClient client = new HttpClient();
        string url = "http://example.com/webservice";
        HttpResponseMessage response = await client.GetAsync(url);
        string result = await response.Content.ReadAsStringAsync();
        Console.WriteLine(result);
    }
}