title: Error: C# The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel
body: <p>I'm trying to make a request via SSL. The certificate is already installed on the machine and it works via browser.</p>
  
  <p>I am using this request:</p>
  
  <pre><code>System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
  byte[] data = encoding.GetBytes(request.Content.OuterXml.ToString());
  string password = "XXXX";
  X509Certificate2 cert = new X509Certificate2("c:\\zzzz.p12", password);
  string key = cert.GetPublicKeyString();
  string certData = Encoding.ASCII.GetString(cert.Export(X509ContentType.Cert));
  
  Uri uri = new Uri(request.Url);
  HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(uri);
  myRequest.Credentials = new NetworkCredential(request.User, request.Password.ToString());
  myRequest.Method = "PUT";
  myRequest.ContentType = request.ContentType;
  myRequest.ContentLength = data.Length;
  myRequest.ClientCertificates.Add(cert);
  
  Stream newStream = myRequest.GetRequestStream();
  newStream.Write(data, 0, data.Length);
  newStream.Close();
  
  System.IO.StreamReader st = new StreamReader(((HttpWebResponse)myRequest.GetResponse()).GetResponseStream());
  </code></pre>
  
  <p>Using this code I get this error:</p>
  
  <blockquote>
    <p>The underlying connection was closed: Could not establish trust
    relationship for the SSL/TLS secure channel. --->
    System.Security.Authentication.AuthenticationException: The remote
    certificate is invalid according to the validation procedure.</p>
  </blockquote>
  
  <p>What is the problem?</p>