How do I handle exceptions in this C # function?

Question

I'm relatively new to C # and .NET, and I'm trying to find out how to better handle exceptions in my code.

Take the following function that I wrote, for example:

  public void SendEmail(string SenderEmail, string SenderDisplayName, IEnumerable<string> RecipientEmails, string Subject, string Message)
    {
        MailMessage message = new MailMessage();

        message.From = new MailAddress(SenderEmail, SenderDisplayName);
        foreach (var recipient in RecipientEmails)
        {
            message.To.Add(recipient);
        }
        message.Subject = Subject;
        message.Body = Message;

        SmtpClient smtpClient = new SmtpClient("192.168.168.182");
        smtpClient.Send(message);
    }
}

If you try to add an email address that is incorrect in Message.From or Message.To, it throws an exception. Right now, my application just crashes and burns when this happens.

Can someone show me a suitable way to handle this exception in this method?

Answer 1

This is the correct way to handle exceptions!

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:

try
{
    SendEmail(SenderEmail, SenderDisplayName, RecipientEmails, Subject, Message);
}
catch (MyMailAddressException ex)
{
    MessageBox.Show(ex.Message);
}

, , MyMailAddressException, , , .

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public enum MailAddressType
{
    Sender,
    Recipient
}

public class MyMailAddressException : Exception
{
    public MailAddressType AddressType { get; set; }
    public string EmailAddress { get; set; }

    public MyMailAddressException(
        string message,
        MailAddressType addressType,
        string emailAddress,
        Exception innerException) : base(message, innerException)
    {
        AddressType = addressType;
        EmailAddress = emailAddress;
    }
}

public void SendEmail(
    string senderEmail,
    string senderDisplayName,
    IEnumerable<string> recipientEmails,
    string subject,
    string message)
{
    using (
        var mailMessage = new MailMessage
                          {
                              Subject = subject, 
                              Body = message
                          })
    {
        try
        {
            mailMessage.From = new MailAddress(
                senderEmail, senderDisplayName);
        }
        catch (FormatException ex)
        {
            throw new MyMailAddressException(
                "Invalid from address", MailAddressType.Sender,
                senderEmail, ex);
        }

        foreach (var recipient in recipientEmails)
        {
            try
            {
                mailMessage.To.Add(recipient);
            }
            catch (FormatException ex)
            {
                throw new MyMailAddressException(
                    "Invalid to address", MailAddressType.Recipient,
                    recipient, ex);
            }
        }

        var smtpClient = new SmtpClient("192.168.168.182");
        smtpClient.Send(mailMessage);
    }
}

MyMailAddressException , , . .

---

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Answer 2

, . , SendMail - , .

Answer 3

. () , MailAddress

:

public bool IsValidEmailAddress(string EmailAddress){
    Regex regEmail = new Regex(@"^[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$");

    if(regEmail.IsMatch(EmailAddress))
        return true;

    return false;
}

if (IsValidEmailAddress(SenderMail)){
    //do stuff to send the mail
}else{
    //return an error to the user interface
}

Answer 4

- , SendMessage() , . .

, , , , SendMessage. :

public void Submit() {
  try {
    SendMessage(emailForm.SenderAddress, emailForm.UserDisplayName,
      emailForm.RecipientEmails, emailForm.Subject, emailForm.MessageBody);
  } catch (MailException e) { // Substitute whichever exception is appropriate to catch here.
    // Tell user that submission failed for specified reasons.
  }
}

Answer 5

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, Try/Catch, , .

Now the fact is that you can turn all this into an exception and completely stop sending e-mail, or you can do it based on TO ADDRESS so that 1 flat address in the list of 100 is not violated by the system. OR you can place it elsewhere (say where you call the function)