以前写抓取网页的代码喜欢用ReadToEnd，因为简单省事，后来发现，在爬取网页的时候，如果网速很慢，ReadToEnd超时的几率很大。使用Read改写后，超时几率大大减小，完整代码如下：

/// <summary>
/// HttpPost
/// </summary>
public static string HttpPost(string url, string data)
{
    byte[] bArr = ASCIIEncoding.UTF8.GetBytes(data);

    // 设置参数
    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
    request.CookieContainer = m_Cookie;
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    request.ContentLength = bArr.Length;
    request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0)";

    Stream postStream = request.GetRequestStream();
    postStream.Write(bArr, 0, bArr.Length);
    postStream.Close();

    //发送请求并获取相应回应数据
    HttpWebResponse response = request.GetResponse() as HttpWebResponse;
    //直到request.GetResponse()程序才开始向目标网页发送Post请求
    Stream responseStream = response.GetResponseStream();
    //返回结果网页（html）代码
    MemoryStream memoryStream = new MemoryStream();
    bArr = new byte[1024];
    int size = responseStream.Read(bArr, 0, (int)bArr.Length);
    while (size > 0)
    {
        memoryStream.Write(bArr, 0, size);
        size = responseStream.Read(bArr, 0, (int)bArr.Length);
        Thread.Sleep(1);
    }
    string content = Encoding.UTF8.GetString(memoryStream.ToArray());
    return content;
}

 代码中Thread.Sleep(1);也可以去掉。