C#发送http请求时，如果服务器返回了错误码和错误消息，按照传统模式就是直接抛出“系统异常”，然后把错误写入日志。这种方式不是很友好，于是调整代码，根据不同的错误码给出友好提示。核心代码如下：

static void Main(string[] args)
{
    try
    {
        WebClient web = new WebClient();
        var str = web.DownloadString("http://localhost:31005/Home/MyTest");
        Console.WriteLine(str);
    }
    catch (WebException ex)
    {
        HttpWebResponse response = (HttpWebResponse)ex.Response;
        Console.WriteLine("错误码:" + (int)response.StatusCode);
        Console.WriteLine("错误码描述:" + response.StatusDescription);

        var stream = response.GetResponseStream();
        stream.Position = 0;
        byte[] bs = new byte[stream.Length];
        stream.Read(bs, 0, bs.Length);
        Console.WriteLine("错误消息:"+ Encoding.UTF8.GetString(bs));
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.ToString());
    }
    Console.ReadLine();

}