Connectig to sFTP Server using SSH public/private key. Error {Invalid private key file.} Using SSH.NET

Firstly I generated the keys using

var keygen = new SshKeyGenerator.SshKeyGenerator(2048);

var privateKey = keygen.ToPrivateKey();
var publicSshKey = keygen.ToRfcPublicKey();

The private key generated the following string:

-----BEGIN RSA PRIVATE KEY-----
MIIEpAIBA... etc.
-----END RSA PRIVATE KEY-----

I'm now trying to create a new Renci.SshNet.PrivateKeyFile object to be used to create the SftpClient object. I tried loading the RSA private Key string in a number of ways similar to:

using (var keyStream = new MemoryStream(Encoding.ASCII.GetBytes(ReturnKey())))
{
    var privateKy = new PrivateKeyFile(keyStream);

}

The method ReturnKey() simply returns a string of the private key -----BEGIN RSA PRIVATE KEY----- etc. I've tried with and without the "-----BEGIN RSA and -----End RSA" and I get the same result:

Error {Invalid private key file.}

I have all the details to connect to sFTP server i.e. User, DNS, Port, Path. which has the public key generated, I just can't load the private key as a start.

This is the first time I've had to connect to sFTP using SSH. Any help would be much appreciated, thank you.

Solution

Looks like it was the way I was adding the private key text; instead I saved the key to a txt file and loaded directly. I think there were additional characters, tabs/returns perhaps in the string from ReturnKey() function, so it would have helped if I added the full code.