string不包含SSIS包中Where，C＃的定义

Question

string不包含SSIS包中Where，C＃的定义，请注意什么？

           MailMessage mail = new MailMessage();
            mail.From = new MailAddress("info@domain.it", "Prova");
            foreach (string recips in email)
            {
                mail.To.Add(recips);
            }
            mail.Subject = "PRova";
            mail.BodyEncoding = System.Text.Encoding.UTF8;
            mail.IsBodyHtml = true;
            mail.Body = messaggio;
            foreach (string itemurl in file)
            {
                System.Net.Mail.Attachment attachment;
                attachment = new System.Net.Mail.Attachment(itemurl);
                mail.Attachments.Add(attachment);
            }
            SmtpClient smtp = new SmtpClient(server);
            smtp.UseDefaultCredentials = false;
            smtp.Credentials = new NetworkCredential("prova", "prova");
            smtp.Send(mail);

Answer 1

Where类的string方法是一种扩展方法，您必须提供它的命名空间。所以你应该添加这个命名空间：

using System.Linq;

Answer 2

我很好奇出了什么问题：

var bytes = Encoding.ASCII.GetBytes(subjectString.Normalize(NormalizationForm.FormKD));
return Encoding.ASCII.GetString(bytes);