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Question

我有一个调用SOAP Web服务的.NET应用程序，它已经运行多年但是几天前它在Windows（Server 2012 R2）安全更新后停止工作（有很多我不知道哪个一）。 Microsoft已发布了一些有关该问题的文章，但所有描述的解决方法都不起作用：

https://support.microsoft.com/en-us/help/3155464/ms16-065-description-of-the-tls-ssl-protocol-information-disclosure-vu

https://support.microsoft.com/en-us/help/3069494/cannot-connect-to-a-server-by-using-the-servicepointmanager-or-sslstre

我正在调用的服务使用SSL3 / TLS1.0，提供程序不能/不会将其升级到TLS1.2。此外，我在旧的Windows 2008R2中测试了我的应用程序，它没有.NET4更新，并且它像之前一样工作。

我的代码：

string url = "https://weblogic_server:7070/app/Service";
string text = "<soapenv:Envelope>...</soapenv:Envelope>";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
ServicePointManager.ServerCertificateValidationCallback = (sender, cert, chain, error) =>
{
    return true;
};
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;
//ServicePointManager.Expect100Continue = false; // did nothing good
//ServicePointManager.UseNagleAlgorithm = false; // did nothing good
byte[] bytes = System.Text.Encoding.ASCII.GetBytes(text);
request.ContentType = "text/xml; encoding='utf-8'";
request.Timeout = 1000000000;
request.ContentLength = bytes.Length;
request.KeepAlive = true;
request.Method = "POST";
using (Stream stm = request.GetRequestStream()) // Exception
{
    using (StreamWriter stmw = new StreamWriter(stm))
    {
        stmw.Write(text);
    }
}
using (StreamReader responseReader = new StreamReader(request.GetResponse().GetResponseStream()))
{
    string resultText = responseReader.ReadToEnd();
    HttpWebResponse resp = (HttpWebResponse)request.GetResponse();
    Console.WriteLine(resp);
    Console.WriteLine(resultText);
}

异常代码是：

System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: The handshake failed due to an unexpected packet format.
   at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)
   at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.ConnectStream.WriteHeaders(Boolean async)
   --- End of inner exception stack trace ---
   at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
   at System.Net.HttpWebRequest.GetRequestStream()

我的问题是：
- 除了文章中描述的内容之外，还有其他方法/解决方法可以使这个调用工作吗？ - 代码在.NET2.0下工作正常，.NET4.0没有更新到.NET4.6，是否有办法强制应用程序使用特定的旧System.dll（从Windows 2008R2机器复制）？我尝试手动添加它作为参考，但CLR总是使用GAC的 - 是否可能超载HttpWebRequest并以某种方式强制它使用SSL3？

感谢。