Web Services and X509

I am getting following error in my web service when using x509 Certificate to authenticate the client.

X509Certificate2 Clnt = new X509Certificate2 (HttpContext.Current.Request.ClientCertificate.Certificate);

The error is System.Web.Services.Protocols.SoapException: Serv开发者_如何学编程er was unable to process request. ---> System.Security.Cryptography.CryptographicException: m_safeCertContext is an invalid handle. at System.Security.Cryptography.X509Certificates.X509Certificate.get_Issuer() at Service.HelloWorld() in c:\MyWorkSpace\SecuredWS\App_Code\Service.cs:line 40 --- End of inner exception stack trace

Can any one put some light on it as why i am getting m_safeCertContext as null.

Regars

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Finally, We solved this issue. If anyone interested to know i can put resolution here.