X509CertificateCollection.Import() doesn't import private Key of my .pem Certificate file

I'm currently implementing an TLS-connection for our communication between our mongo database (Version 4.2) and our software. This is my method I use to import all certificates from a file.

/// <summary> Reads an certificate file </summary>
		/// <param name="path"> Path to the certificate </param>
		/// <param name="password"> Password to access the file </param>
		/// <returns></returns>
		public static X509Certificate2Collection ReadCertificateFile(string path, string password) {
			var certificateCollection = new X509Certificate2Collection();

			certificateCollection.Import(path, password, X509KeyStorageFlags.Exportable);

			return certificateCollection;
		}

It works fine with every certificate format except .pem. As far as I can say the private key is in the PEM file but cannot be read.

I used openssl to convert the .pfx file to a .pem file with and without password. Neither of which worked because the private key wasn't imported. I installed .net 6 because they have implemented new methods to import pem files but the same happend there too.

I thank in advance everyone who is trying to help me.

I figured it out myself. Only certificate files in the PKCS12 format can be read with the private key.
I found in this project the solution to my problem: Create X509Certificate with Private Key from PEM File. The article explains how to extract the certificate and private key separately and then assign the private key to the X509Certificate instance.

> I installed .net 6 because they have implemented new methods to import pem files

Those new methods are new, not modifying the existing ones. To load a cert and key from two PEM files is with X509Certificate2.ImportFromPemFile(pathToCert, pathToKey); if they're in the same file you can either specify the same value twice or leave off the second parameter (X509Certificate2.ImportFromPemFile(pathToJoinedPem))