要在ASP.NET Boilerplate中发送带附件的电子邮件，可以按照以下步骤进行操作：

1. 添加所需的NuGet包：

   • Abp.MailKit：用于发送电子邮件
   • MimeKit：用于创建和处理电子邮件消息

2. 在应用程序的模块中注册邮件功能。在YourProjectName.Core项目中，创建一个名为YourProjectNameCoreModule.cs的类，并添加以下代码：

using Abp.MailKit;
using Abp.MailKit.Configuration;
using Abp.Modules;

namespace YourProjectName
{
    [DependsOn(typeof(AbpMailKitModule))]
    public class YourProjectNameCoreModule : AbpModule
    {
        public override void PreInitialize()
        {
            Configuration.Modules.AbpMailKit().EnableImap().EnableSmtp();
        }
    }
}

3. 在应用程序的配置文件中设置邮件参数。在YourProjectName.Web项目中的appsettings.json文件中，添加以下配置：

"App": {
  "Email": {
    "DefaultFromAddress": "your-email@example.com",
    "DefaultFromDisplayName": "Your Name",
    "Smtp": {
      "Host": "smtp.example.com",
      "Port": 587,
      "UserName": "your-email@example.com",
      "Password": "your-email-password",
      "EnableSsl": true
    }
  }
}

4. 创建一个名为EmailSender的类，并注入IEmailSender接口。在YourProjectName.Core项目中创建一个名为EmailSender.cs的类，并添加以下代码：

using Abp.Mail;
using Abp.Net.Mail.Smtp;
using MimeKit;
using System.Threading.Tasks;

namespace YourProjectName
{
    public class EmailSender : IEmailSender
    {
        private readonly ISmtpEmailSender _smtpEmailSender;

        public EmailSender(ISmtpEmailSender smtpEmailSender)
        {
            _smtpEmailSender = smtpEmailSender;
        }

        public async Task SendEmailAsync(string toEmail, string subject, string body, string[] attachments)
        {
            var message = new MimeMessage();
            message.From.Add(new MailboxAddress("Your Name", "your-email@example.com"));
            message.To.Add(new MailboxAddress("", toEmail));
            message.Subject = subject;
            message.Body = new TextPart("plain") { Text = body };

            foreach (var attachmentPath in attachments)
            {
                var attachment = new MimePart()
                {
                    Content = new MimeContent(System.IO.File.OpenRead(attachmentPath)),
                    ContentDisposition = new ContentDisposition(ContentDisposition.Attachment),
                    ContentTransferEncoding = ContentEncoding.Base64,
                    FileName = System.IO.Path.GetFileName(attachmentPath)
                };

                message.Attachments.Add(attachment);
            }

            await _smtpEmailSender.SendAsync(message);
        }
    }
}

5. 注册EmailSender类。在YourProjectName.Core项目中的YourProjectNameCoreModule.cs文件的PreInitialize方法中，添加以下代码：

Configuration.Modules.AbpCore().Register();
IocManager.Register();

6. 在需要发送电子邮件的地方使用IEmailSender接口。在您的应用程序的任何地方（例如控制器、应用程序服务等），注入IEmailSender接口，并使用SendEmailAsync方法发送电子邮件。例如：

public class YourAppService : ApplicationService
{
    private readonly IEmailSender _emailSender;

    public YourAppService(IEmailSender emailSender)
    {
        _emailSender = emailSender;
    }

    public async Task SendEmailWithAttachmentAsync(string toEmail, string subject, string body, string attachmentPath)
    {
        await _emailSender.SendEmailAsync(toEmail, subject, body, new string[] { attachmentPath });
    }
}

这样，您就可以在ASP.NET Boilerplate中发送带附件的电子邮件了。只需使用IEmailSender接口，并调用SendEmailAsync方法即可发送电子邮件。