c#代码的400个错误请求

在这一小段代码上抛出一个错误异常，但我不知道为什么/在哪里。这是相当新的，所以任何帮助将不胜感激

private void GetServiceData(string url)
{
    try
    {
        if (!string.IsNullOrEmpty(this.Service) && !string.IsNullOrEmpty(url))
        {
            string data = string.Empty;
            string name = string.Format("{0}Data", this.Service);
            using (WebClient client = new WebClient())
            {
                data = client.DownloadString(url);
            }
            Page.ClientScript.RegisterHiddenField(name, data);
        }
    }
    catch (Exception ex)
    {
        Shared.Utilities.ExceptionLog.WriteExceptionToLog(ex, "CourseFinderServiceControl.GetServiceData()");
    }
}