How do I use abstract classes in a 3-tier solution?

Question

My immediate issue is that currently I have a 3 tier solution (Presentation.aspx.vb calls BusinessLayer.vb which calls DataAccessLayer.vb). However, I want to make BusinessLayer and DataAccessLayer.vb abstract classes because several Webforms will use have the same functionality.

So I currently am doing this (no abstract classes):

'Presentation Layer (pseudocode)

public sub checkUser(byval userName as string, byval dept as string)

   dim isGood as boolean = BL.checkUserAccess(userName, dept)

   'some more code
   'change properties of webcontrols, etc

end sub



'Business Layer (pseudocode)

public function checkUserAccess(byval name as string, byval group as string) as boolean

   dim accessObject as dataObject =  DAL.checkPermissions(name, group)

   if accessObject.isHighAccess then
      'some code
   else
      'some other code      
   end if 

end function



'Data Access Layer (pseudocode)

public function checkPermissions(byval userid as string, byval section as string) as dataObject

   'some code

end function

However can I still have this structure if I add abstract classes?

For instance:

'Presentation Layer (pseudocode)

public sub checkUser(byval userName as string, byval dept as string)

   dim isGood as boolean = instOne_BL.checkUserAccess(userName, dept)

   'some more code
   'change properties of webcontrols, etc

end sub



'Business Layer (pseudocode)

public class instOne_BL inhertis BL

   public function checkUserAccess(byval name as string, byval group as string) as boolean

      base.checkUserAccess(name, group)
      instOne_DAL.checkPermissions(name, group)

   end function
end class      


'Data Access Layer (pseudocode)

public class instOne_DAL inherits DAL

   public function checkPermissions(byval userid as string, byval section as string) as dataObject

      base.checkPermissions(userid, section)

   end function
end class

Are you interested in using an abstract class (implies the use of MustInherit) or just Inheriting a class? Your example looks like simple inheritance to me. — Casey Wilkins, Feb 01 '12 at 16:55
Well inheriting the abstract class and using it in my 3-tier setup is what I'm interested in. If that makes sense. — dotnetN00b, Feb 01 '12 at 17:10
What is the communication mechanism between the layers? The answer will vary depending on whether it is .Net remoting, WCF, web services, or something else. — competent_tech, Feb 01 '12 at 17:26
ASP.Net 3.5, ADO.NET 3.5: just datatables, and dataadapters. No ASMX, WCF, or .Net remoting. — dotnetN00b, Feb 01 '12 at 18:21

score 1 · Answer 1 · answered Feb 01 '12 at 17:32

If you use .Net remoting as the communication layer between the layers, then this is no problem at all (it's just like calling a method in another class within the current layer).

If you use WCF, then this will also work, buy you need to do a little more work. The base/abstract class must be decorated with KnownType attributes of all inheriting classes that you expect to pass.

If you use web services, then this is not possible without playing some games. For example, you would need to serialize the object into a string using the binary serializer and then deserialize it on the other end.

How do I use abstract classes in a 3-tier solution?

1 Answers1