Hello,
I'm trying to work with inheritance in classes. Below in my
namespace I'd like to have a base email class and 2 other classes
that inherit the base constructor but send different subjects and
subject bodies. I'm not sure how to do this, whether I should use
parameters for the subject and subject bodies or private variables,
maybe you know or maybe what I'm trying to doesn't sound right.

Imports Microsoft.VisualBasic
Imports System.Net.Mail
Namespace Email

     Public Class SendEmail

         Sub New(ByVal sendTo As String, ByVal sendFrom As String, ByVal sendSubject As String, ByVal sendBody As String)

             Dim mailObj As New MailMessage(sendTo, sendFrom, sendSubject, sendBody)
             mailObj.Subject = sendSubject
             mailObj.Body = sendBody
             mailObj.IsBodyHtml = True
             Dim smtp As New SmtpClient
             smtp.Send(mailObj)

         End Sub
     End Class

     Public Class AccountCreated

         Sub New(ByVal sendTo As String, ByVal sendFrom As String, ByVal sendSubject As String, ByVal sendBody As String)

             Dim mailObj As New MailMessage(sendTo, sendFrom, sendSubject, sendBody)
             mailObj.Subject = sendSubject
             mailObj.Body = sendBody
             mailObj.IsBodyHtml = True
             Dim smtp As New SmtpClient
             smtp.Send(mailObj)

         End Sub
     End Class

     Public Class Checkout

         Sub New(ByVal sendTo As String, ByVal sendFrom As String, ByVal sendSubject As String, ByVal sendBody As String)

             Dim mailObj As New MailMessage(sendTo, sendFrom, sendSubject, sendBody)
             mailObj.Subject = sendSubject
             mailObj.Body = sendBody
             mailObj.IsBodyHtml = True
             Dim smtp As New SmtpClient
             smtp.Send(mailObj)

         End Sub
     End Class
End Namespace


thanks,
Michael.

Hi Michael,

Why are you using constructors for sending out e-mail? Personally, I think that's a flawed design. Constructors are used to instantiate new instances of objects that you work with afterwards. In your situation, it seems you're done with the object after you constructed it, right? I think you're much better off with a few smart overloads, like this: This code allows you to call various flavors of the Send method, passing in detailed information as you see fit. It's just a simple example, but hopefully it puts you in the right direction. Important keywords here are Shared methods and overloads.

If this isn't what you're after, can you describe in a bit more detail what you're trying to accomplish?

Imar

(Edit: added the Shared keyword to the code)

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
Author of ASP.NET 2.0 Instant Results and Beginning Dreamweaver MX / MX 2004
Want to be my colleague? Then check out this post.

Hi Imar,
First of all, is it not good practice to use construtors for every class you define?
Secondly where are the shared methods in your class?

I understand overloading the methods, but what I am trying to create is a class that will send 3 different emails, a standard email, an email to admin, and an email when a product has been bought.
I would like to encapsulate the sendto, send subject, and send message in the classes so that they can be easily changed from one central point.

I'd like only the standard email to have a parameter for the subject so that the sendto email can be defined as a private member variable - so that any pages that use this class and method will go to the same email.

I'd like the second email method that goes to admin to use a private member variable for the email address, the email subject and email message.

And I'd like the third email method that goes to admin on purchase to use a private member variable for both the email and subject and message body.

Does this make sense?

thanks,
Michael.

On the contrary: it is good practice. If you leave out the constructor, the compile will add one for you.

However, IMO, it's odd that a constructor sends a message. I think a constructor should do nothing more than construct the object and initialize some data. Then a method should do the work.

What happens when a developer using your class does this:

Dim myObject As New MailClass()

As this point, he or she may think that all they did was create a new object, but in the background already an e-mail message have been sent. Personally, I would do something like this:

Dim myObject As New MailClass()
myObject.Send()

This creates an object, possibly defaulting some variables, fields etc. Then a developer has to call Send explicitly.

By creating classes that inherit from your base class, the model stays the same. You can do this:

Dim myObject As New SpecializedMailClass()
myObject.Send()

and things will still work.

I changed my earlier post and added the Shared keyword that I had forgotten. With the shared keyword you can do this:

SpecializedMailClass.Send(SomeValue, SomeOtherValue)

or

SpecializedMailClass.Send(SomeValue)

or even:

SpecializedMailClass.Send()

Then the shorter Send overloads define the default values for the parameters for the extensive overloaded version.

Does this help?

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
Author of ASP.NET 2.0 Instant Results and Beginning Dreamweaver MX / MX 2004
Want to be my colleague? Then check out this post.

Hi Imar,
thanks that makes sense regarding using the constructor to initialize private member variables and the public shared methods.

I'm still having difficulty with the inheritance issues though I'll try and work out a code example myself and then maybe repost it.

thanks again.

Good luck. You know where to find us if you need more help...

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
Author of ASP.NET 2.0 Instant Results and Beginning Dreamweaver MX / MX 2004
Want to be my colleague? Then check out this post.