c# how to send ios notification via dotAPNS (nuget package) / how to read a certificate in c#?

Question

The below code is in my c# api project in the notification service. I am using the dotAPNS nuget package to enable ios notifications. However, when I try to send the request I get an error thrown which has to deal with the CertContent contents. I feel like I am not doing it correctly and the error reassures that doubt. Can you help me figure out what I am doing wrong?

            var cer = HttpContext.Current.Server.MapPath("../../Security/distribution.cer");

            var x509 = new X509Certificate2(File.ReadAllBytes(cer)).ToString();


            var options = new ApnsJwtOptions()
            {
                BundleId = "bundleID",
                CertContent = x509,
                KeyId = "keyID",
                TeamId = "teamID"
            };

        var apns = ApnsClient.CreateUsingJwt(new HttpClient(new WinHttpHandler()), options);
        var push = new ApplePush(ApplePushType.Alert)
            .AddAlert("title", model.UserName + ", commented on your post.")
            .AddToken("deviceToken");

The below is the exception message I get when it gets to ApplePush:

The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters.

I thank you in advance!