C# HttpWebRequest中出现错误

我有一个使用HttpWebRequest的WP7应用程序。应用程序尝试从服务器获取一些xml数据。但是当我试图获取详细信息时，出现了一个运行时错误。错误发生在

HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult);

在ReadCallback方法中。错误消息为“远程服务器返回错误：NotFound.”，错误状态为“UnknowError”

代码如下

private void SendPostRequest(byte[] userDetails)
{
    string url = "http://myWebsite.com";
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(url, UriKind.Absolute));

    string auth = "Basic " + Convert.ToBase64String(userDetails);
    request.Accept = "*/**";
    request.ContentType = "application/x-www-form-urlencoded";
    request.UseDefaultCredentials = true;
    request.Headers[HttpRequestHeader.Authorization] = auth;
    request.Headers[HttpRequestHeader.ContentLength] = Convert.ToString(0);
    request.Method = "POST";

    request.BeginGetResponse(new AsyncCallback(ReadCallBack), request);
}

private void ReadCallBack(IAsyncResult asyncResult)
{
    HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
    try
    {
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult);
        using (StreamReader streamReader1 = new StreamReader(response.GetResponseStream()))
        {
            string resultString = streamReader1.ReadToEnd();
        }
    }
    catch (WebException ex)
    {
        string errorMessage = ex.Message;
        string errorStatus = ex.Status.ToString();
    }
}

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不幸的是，“NotFound”响应会针对各种错误返回。您是如何验证服务器是否已启动、URI是否正确（没有拼写错误）以及是否可以通过电话访问它的？这是我的错，我使用了byte[]byteArray=System.Text.Unicode.GetBytes（uIdPass）；而不是byte[]byteArray=System.Text.UTF8Encoding.UTF8.GetBytes（uIdPass）；