Mutual SSL Handshake in C# using HTTPWebRequest and TLS1.2

sslhandshake.cs

private static void FromFile()
{   
 // You have to use certificate.p12 or certificate.pfx that contains  private key. These extensions represent PKCS#12 standard. There can also be whole certificate chain included in these files
 var certificatefilePath = "CertificateFile.pfx";
 var certpwd = "password";
 var URL = "Host_URL";
 X509Certificate cert = new X509Certificate(certificatefilePath,certpwd);

 var webrequest = WebRequest.Create(URL) as HttpWebRequest;

 ServicePointManager.Expect100Continue = true;           
 ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072; //TLS 1.2
 ServicePointManager.ServerCertificateValidationCallback = ((object obj, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) => true);

 webrequest.ClientCertificates.Add(cert);

 webrequest.Credentials = CredentialCache.DefaultNetworkCredentials;
 webrequest.Method = WebRequestMethods.Http.Get;
 webrequest.ContentType = "application/json; charset=utf-8";

 var responseStream = webrequest.GetResponse().GetResponseStream();
}

Reference 1