I have this piece of code whose equivalents I have found in multiple places. But it is returning null when I am using it. 

```
  using Org.BouncyCastle.OpenSsl;
  using Org.BouncyCastle.Crypto;
  using Org.BouncyCastle.Security;  

 string aToBeEncrypted= "asdfghikoksadjfkjsdfjsljfsadjf";
 string pemFilename = @"M:\ConnectivityPackage_meltemi_KeyStore.pem";

 byte[] plaintext = System.Text.Encoding.UTF8.GetBytes(aToBeEncrypted);

 AsymmetricCipherKeyPair keyPair;

 using (var reader = File.OpenText(pemFilename))
    keyPair = (AsymmetricCipherKeyPair)new PemReader(reader).ReadObject();

```

keyPair is a null object. What is it that I am doing wrong or is it something with the pem file?