Signing certificates

BouncyCastle C# has support in the Org.BouncyCastle.OpenSsl namespace for writing a certificate out in PEM format directly:

Org.BouncyCastle.X509.X509Certificate cert = ...;
using (FileStream fs = ...)
{
    TextWriter w = new StreamWriter(fs);
    PemWriter pw = new PemWriter(w);
    pw.WriteObject(cert);
    pw.Writer.Close();
}