C#在http请求中未接收完整的HTML

我正在使用此代码对HTML页面发出请求:

public static String MakeHttpRequest(String url)
{
    try
    {
        HttpWebRequest httpWReq = (HttpWebRequest)WebRequest.Create(url);
        HttpWebResponse response = (HttpWebResponse)httpWReq.GetResponse();
        string responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

        return responseString;
    }
    catch (Exception e)
    {
        return null;
    }
}

我注意到,有时我从它收到的不是完整的HTML代码,而是它的一半(我通过它识别它有时 responseString