首先，在Visual Studio中创建一个新的ASP.NET Core MVC项目。

添加一个名为"QRCodeGenerator"的类，用于生成唯一的预订QR码。可以使用QRCode.NET库来生成QR码。示例代码如下：

using System.Drawing;
using QRCoder;

public static class QRCodeGenerator
{
    public static Bitmap Generate(string text)
    {
        var qrGenerator = new QRCodeGenerator();
        var qrCodeData = qrGenerator.CreateQrCode(text, QRCodeGenerator.ECCLevel.Q);
        var qrCode = new QRCode(qrCodeData);
        var qrCodeImage = qrCode.GetGraphic(20);
        return qrCodeImage;
    }
}

创建一个名为“BookingConfirmationEmail”的服务，该服务用于创建和发送预订确认电子邮件，并将唯一的QR码作为附件添加到电子邮件中。示例代码如下:

using System.IO;
using System.Net;
using System.Net.Mail;
using System.Threading.Tasks;

public class BookingConfirmationEmail
{
    private readonly string _smtpServer;
    private readonly int _smtpPort;
    private readonly string _smtpUsername;
    private readonly string _smtpPassword;
    private readonly string _fromAddress;

    public BookingConfirmationEmail(string smtpServer, int smtpPort, string smtpUsername, string smtpPassword, string fromAddress)
    {
        _smtpServer = smtpServer;
        _smtpPort = smtpPort;
        _smtpUsername = smtpUsername;
        _smtpPassword = smtpPassword;
        _fromAddress = fromAddress;
    }

    public async Task SendBookingConfirmationEmailAsync(string toAddress, string qrCodeText)
    {
        var subject = "Booking Confirmation";
        var body = "Thank you for your booking.";
        var qrCodeImage = QRCodeGenerator.Generate(qrCodeText);

        using (var memoryStream = new MemoryStream())
        {
            qrCodeImage.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Png);
            memoryStream.Position =