如何通过同步方法使用SendGrid C#库发送电子邮件？

using SendGrid;
using SendGrid.Helpers.Mail;

var message = new SendGridMessage();
message.SetFrom(new EmailAddress("sender@example.com", "Sender Name"));
message.AddTo(new EmailAddress("recipient@example.com", "Recipient Name"));
message.SetSubject("Email Subject");
message.AddContent(MimeType.Text, "Email Content");

var bytes = File.ReadAllBytes("path/to/attachment.pdf");
var file = Convert.ToBase64String(bytes);
message.AddAttachment("attachment.pdf", file);

var apiKey = "YOUR_SENDGRID_API_KEY";
var client = new SendGridClient(apiKey);

var response = client.SendEmailAsync(message).Result;
if (response.StatusCode == System.Net.HttpStatusCode.Accepted)
{
    Console.WriteLine("Email sent successfully.");
}
else
{
    Console.WriteLine("Failed to send email. Error: " + response.StatusCode);
}