I'm new to ASP and I'm using csharp inside my html page. This is my code, clientcert is a base64 encoded cert. I can print that out on the screen fine. I can also print out a to the screen and know it's of type byte[]. However I get an error when I do the following.

<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Security.Cryptography.X509Certificates" %>
<%@ Import Namespace="System.Text" %>
<%@ Page Language="c#"%>


<%
string certPem = Request.Headers["ClientCert"];
System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
byte[] a = encoding.GetBytes(certPem);
X509Certificate2 cer = new X509Certificate2(a);
%>

[CryptographicException: Cannot find the requested object.
]
Exception Details: System.Security.Cryptography.CryptographicException: 
Cannot find the requested object.

I'm wondering, why can I get a x509 object fine -- it works when doing new x509Certificate2(); with no arguments, but when passing it a byte array it just errors out.