/// <summary>
/// 根据Url获得源文件内容
/// </summary>
/// <param name="url">合法的Url地址</param>
/// <returns></returns>
public static string GetSourceTextByUrl(string url)
{
    WebRequest request = WebRequest.Create(url);
    request.Timeout = 20000;//20秒超时
    WebResponse response = request.GetResponse();
    Stream resStream = response.GetResponseStream();
    StreamReader sr = new StreamReader(resStream);
    return sr.ReadToEnd();
}