Hi there,
I want to begin understanding how class libraries are written under
VB.NET and how can i call them under my executable project. For
example think an arithmetic calculator includes only plus, minus,
division, multiplying functions.
Yes it may not be necessary but how can i seperate each arithmetic
funtion into per class library and call them under my executable
project?
Thanks...
You create a class library project containing your classes. Make the
classes you want to expose, public as well as the methods you want to
be visible out side of the assembly.
For example the class we want to expose in the DLL:
Option Strict On
Option Explicit On
Public Class Calculator
Public Function Add(ByVal first As Integer, ByVal second As
Integer) As Integer
Return first + second
End Function
Public Function Subtract(ByVal first As Integer, ByVal second As
Integer) As Integer
Return first - second
End Function
End Class
Now,in the project we want to use this class we need to make a
reference to the dll. This can be done in several ways - but in this
case, I'm going to use what's called a project reference. I'm going
to go to the solution explorer right click on the solution -> add ->
Existing Project, and select my dll's project file. Once it's added
to the solution, I'm going to go to the solution explorer and right
click on the application I'm going to use the object from and select
add reference. Once the add reference dialog comes up I'm going to
select the projects tab and double click on my dll project.
Once I do that, I can now add the imports statement - which will be
for the namespace i put my object in, in this case I let it default,
but in practice you should probably come up with a standardized way of
doing your namespaces. I tend to do something like this
companyname.category.specificfunctionalgroup. So they might be, if my
company was ABC something like: ABC.Utilities.WordInterop Anway, this
is the statement I add to my console app:
Option Strict On
Option Explicit On
Imports ClassLibrary1 ' this is the namespace containing my caculator
object
Module Module1
Sub Main()
End Sub
End Module
From then on we can just use it:
Option Strict On
Option Explicit On
Imports ClassLibrary1
Module Module1
Sub Main()
Dim calc As New Calculator
Console.WriteLine("============== Adding ==============")
Console.WriteLine("4 + 3 = {0}", calc.Add(4, 3))
Console.WriteLine("6 + 6 = {0}", calc.Add(6, 6))
Console.WriteLine("-2 + 5 = {0}", calc.Add(-2, 5))
Console.WriteLine("====================================")
Console.WriteLine()
Console.WriteLine("=========== Subtracting ===========")
Console.WriteLine("2 - 2 = {0}", calc.Subtract(2, 2))
Console.WriteLine("5 - 8 = {0}", calc.Subtract(5, 8))
Console.WriteLine("100 - 3 = {0}", calc.Subtract(100, 3))
Console.WriteLine("====================================")
End Sub
End Module
Anyway - I hope that helps. You can also, use the browse tab and
browse to the actual compiled dll. But, that can cause path issues
especially in team development. Though, project references aren't
always practicle either. The other way to reference the object is to
put it in the gac - which means strong nameing the assembly. And then
you will see it on the .NET references tab.
