c# SSL请求-证书验证

我正在向HTTPS请求添加一个自签名的X509证书。

request.ClientCertificates.Add(new X509Certificate(@"key.pfx", ""));

与nginx对话，使用:

 ssl_verify_client on;

因为它是自签名的，我在证书签名链上得到一个错误。所以我告诉c#忽略它。(执行lambda并返回true)

 ServicePointManager.ServerCertificateValidationCallback += 
                                (sender, cert, chain, sslPolicyErrors) => true;

然而，我从nginx得到以下错误:

400 Bad Request
No required SSL certificate was sent
nginx/1.0.5

谁能解释一下为什么会发生这种情况?或者我怎么能找到原因?
我目前的想法:证书正在从http客户端删除，因为它是自签名的?

c# 的一些诊断输出

Step into: Stepping over method without symbols 'System.Net.Security.SecureChannel.VerifyRemoteCertificate'
System.Net Information: 0 : [5516] SecureChannel#31534420 - Remote certificate has errors:
System.Net Information: 0 : [5516] SecureChannel#31534420 -     A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider.
System.Net Information: 0 : [5516] SecureChannel#31534420 - Remote certificate was verified as valid by the user.

欢迎任何帮助!谢谢,克里斯。