VB.Net Tutorial/Class Module/Interface

Implement Interface

<source lang="vbnet">Option Strict On

Imports System
Interface Printable
    Sub Read( )
    Sub Write(ByVal obj As Object)
    Property Status( ) As Integer
End Interface 
Public Class Document
    Implements Printable
    Public Sub New(ByVal s As String)
        Console.WriteLine("Creating document with: {0}", s)
    End Sub
    Public Sub Read( ) Implements Printable.Read
        Console.WriteLine("Implementing the Read Method for Printable")
    End Sub
    Public Sub Write(ByVal o As Object) Implements Printable.Write
        Console.WriteLine("Implementing the Write Method for Printable")
    End Sub
    Public Property Status( ) As Integer Implements Printable.Status
        Get
            Return myStatus
        End Get
        Set(ByVal Value As Integer)
            myStatus = Value
        End Set
    End Property
    Private myStatus As Integer = 0
End Class
Class Tester
    Public Shared Sub Main( )
        Dim doc As New Document("Test Document")
        doc.Status = -1
        doc.Read( )
        Console.WriteLine("Document Status: {0}", doc.Status)
    End Sub 
End Class</source>

Creating document with: Test Document
Implementing the Read Method for Printable
Document Status: -1

Inheritance And Interfaces

<source lang="vbnet">Imports System Imports System.Collections Public Interface Printable

 ReadOnly Property Print() As Integer

End Interface Public Class Money

 Implements Printable
 Protected mTransactions As New ArrayList()
 ReadOnly Property Print() As Integer Implements Printable.Print
   Get
     Return mTransactions.Count
   End Get
 End Property
 Public Overridable ReadOnly Property Balance() As Double
   Get
     Dim result As Double = 0.0
     Dim i As Integer
     For i = 0 To mTransactions.Count - 1
       result += CDbl(mTransactions(i))
     Next
     Return result
   End Get
 End Property
 Public Sub Add(ByVal amount As Double)
   mTransactions.Add(amount)
 End Sub
 Public Sub Subtract(ByVal amount As Double)
   mTransactions.Add(-amount)
 End Sub

End Class Public Class MyMoney

 Inherits Money
 Public Overrides ReadOnly Property Balance() As Double
   Get
     Return MyBase.Balance - Print * 2
   End Get
 End Property

End Class Module Test

 Sub Main()
   Dim acc1 As New Money()
   acc1.Add(200)
   acc1.Subtract(40)
   acc1.Add(30)
   Console.Write("count: {0}, ", acc1.Print)
   Console.WriteLine("balance: {0}", acc1.Balance)
   Dim acc2 As New MyMoney()
   acc2.Add(200)
   acc2.Subtract(40)
   acc2.Add(30)
   Console.Write("count: {0}, ", acc2.Print)
   Console.WriteLine("balance: {0}", acc2.Balance)
 End Sub

End Module</source>

count: 3, balance: 190
count: 3, balance: 184

Interface Inherits Interface

<source lang="vbnet">Imports System

Interface Printable
    Sub Read( )
    Sub Write(ByVal obj As Object)
    Property Status( ) As Integer
End Interface "Printable
Interface Zippable
    Sub Zip( )
    Sub Unzip( )
End Interface "Zippable
Interface Zippable2 
Inherits Zippable
    Sub Email( )
End Interface 
Public Class Document 
Implements Zippable2, Printable
  Public Sub New(s As String)
    Console.WriteLine("Creating document with: {0}", s)
End Sub
    Public Sub Read( ) Implements Printable.Read
    Console.WriteLine("Implementing the Read Method for Printable")
    End Sub "Read
    Public Sub Write(ByVal o As Object) Implements Printable.Write
        Console.WriteLine( _
              "Implementing the Write Method for Printable")
    End Sub "Write
    Public Property Status( ) As Integer Implements Printable.Status
        Get
            Return myStatus
        End Get
        Set(ByVal Value As Integer)
            myStatus = Value
        End Set
    End Property
    Public Sub Zip( ) Implements Zippable.Zip
        Console.WriteLine("Implementing Zip")
    End Sub
    Public Sub Unzip( ) Implements Zippable.Unzip
        Console.WriteLine("Implementing Unzip")
    End Sub
    Public Sub Email( ) Implements Zippable2.Email
        Console.WriteLine("Implementing Email")
    End Sub 
    Private myStatus As Integer = 0
End Class "Document
Class Tester
    Shared Sub Main( )
        Dim doc As New Document("Test Document")
        If TypeOf doc Is Printable Then
            Dim isDoc As Printable = doc
            isDoc.Read( )
        Else
            Console.WriteLine("Could not cast to Printable")
        End If
        If TypeOf doc Is Zippable2 Then
            Dim ilDoc As Zippable2 = doc
            Console.Write("Calling both Zippable and ")
            Console.WriteLine("Zippable2 methods...")
            ilDoc.Zip( )
            ilDoc.Email( )
        Else
            Console.WriteLine("Could not cast to Zippable2")
        End If
        If TypeOf doc Is Zippable Then
            Dim icDoc As Zippable = doc "
            Console.WriteLine( _
               "Treating the object as Zipible... ")
            icDoc.Zip( )
        Else
            Console.WriteLine("Could not cast to Zippable")
        End If
    End Sub
End Class</source>

Creating document with: Test Document
Implementing the Read Method for Printable
Calling both Zippable and Zippable2 methods...
Implementing Zip
Implementing Email
Treating the object as Zipible...
Implementing Zip

Interface with Property

<source lang="vbnet">Class Tester

  Shared Sub Main()
     Dim tree As New Plant(1976)
     Dim person As New Animal("B", "J", 1983)
     Dim iAgeArray As Markable() = New Markable(1) {}
     iAgeArray(0) = tree
     iAgeArray(1) = person
     Console.WriteLine(tree.ToString() & ": " & _
        tree.Name & vbCrLf & "Age is " & tree.Age)
     Console.WriteLine(person.ToString() & ": " & _
        person.Name & vbCrLf & "Age is " & person.Age)
     Dim ageReference As Markable
     For Each ageReference In iAgeArray
        Console.WriteLine(ageReference.Name & ": " & _
           "Age is " & ageReference.Age)
     Next
  End Sub " Main

End Class

Public Interface Markable

  ReadOnly Property Age() As Integer
  ReadOnly Property Name() As String

End Interface Public Class Animal

  Implements Markable
  Private mYearBorn As Integer
  Private mFirstName As String
  Private mLastName As String
  Public Sub New(ByVal firstNameValue As String, _
     ByVal lastNameValue As String, _
     ByVal yearBornValue As Integer)
     mFirstName = firstNameValue
     mLastName = lastNameValue
     mYearBorn = yearBornValue
  End Sub " New
  ReadOnly Property Age() As Integer _
     Implements Markable.Age
     Get
        Return Date.Now.Year - mYearBorn
     End Get
  End Property " Age
  ReadOnly Property Name() As String _
     Implements Markable.Name
     Get
        Return mFirstName & " " & mLastName
     End Get
  End Property " Name

End Class Public Class Plant

  Implements Markable
  Private mRings As Integer
  Public Sub New(ByVal yearPlanted As Integer)
     mRings = Date.Now.Year - yearPlanted
  End Sub " New
  Public Sub AddRing()
     mRings += 1
  End Sub " AddRing
  ReadOnly Property Age() As Integer _
     Implements Markable.Age
     Get
        Return mRings
     End Get
  End Property " Age
  ReadOnly Property Name() As String _
     Implements Markable.Name
     Get
        Return "Tree"
     End Get
  End Property " Name

End Class</source>

Plant: Tree
Age is 31
Animal: B J
Age is 24
Tree: Age is 31
B J: Age is 24

Interface with two methods

<source lang="vbnet">Interface Speak

   Sub GoodMorning()
   Sub GoodEvening(ByVal CurrentDate As DateTime)

End Interface Class English

   Implements Speak
   Public Sub GoodMorning() Implements Speak.GoodMorning
       Console.WriteLine("Good morning!")
   End Sub
   Public Sub GoodEvening(ByVal CurrentDate As DateTime) Implements Speak.GoodEvening
       Console.WriteLine("Good evening -- it is now " & CurrentDate)
   End Sub

End Class Class Spanish

   Implements Speak
   Public Sub GoodMorning() Implements Speak.GoodMorning
       Console.WriteLine("Buenos Dias!")
       Console.WriteLine(Now())
   End Sub
   Public Sub GoodEvening(ByVal CurrentDate As DateTime) Implements Speak.GoodEvening
       Console.WriteLine("Buenas noches -- La fetcha y hora son " & CurrentDate)
   End Sub

End Class

Module Module1

   Sub Main()
       Dim Hello As New English()
       Dim Hola As New Spanish()
       Hello.GoodMorning()
       Hello.GoodEvening(Now())
       Hola.GoodMorning()
       Hola.GoodEvening(Now())
   End Sub

End Module</source>

Good morning!
Good evening -- it is now 11/05/2007 9:29:46 PM
Buenos Dias!
11/05/2007 9:29:46 PM
Buenas noches -- La fetcha y hora son 11/05/2007 9:29:46 PM

One Class implements two interfaces

<source lang="vbnet">Option Strict On

Imports System
    Interface Printable
        Sub Read( )
        Sub Write(ByVal obj As Object)
        Property Status( ) As Integer
    End Interface "Printable
    Interface Zippable
        Sub Zip( )
        Sub Unzip( )
    End Interface
    Public Class Document
        Implements Zippable, Printable
        Public Sub New(ByVal s As String)
            Console.WriteLine("Creating document with: {0}", s)
        End Sub "New
        Public Sub Read( ) Implements Printable.Read
            Console.WriteLine("Implementing the Read Method for Printable")
        End Sub "Read
        Public Sub Write(ByVal o As Object) Implements Printable.Write
            Console.WriteLine( _
              "Implementing the Write Method for Printable")
        End Sub "Write
   Public Property Status( ) As Integer Implements Printable.Status
            Get
                Return myStatus
            End Get
            Set(ByVal Value As Integer)
                myStatus = Value
            End Set
        End Property
        Public Sub Zip( ) Implements Zippable.Zip
            Console.WriteLine("Implementing Zip")
        End Sub
        Public Sub Unzip( ) Implements Zippable.Unzip
            Console.WriteLine("Implementing Unzip")
        End Sub
        Private myStatus As Integer = 0
    End Class 
    Class Tester
        Shared Sub Main( )
            Dim doc As New Document("Test Document")
            doc.Status = -1
            doc.Read( )
            doc.Zip( )
            Console.WriteLine("Document Status: {0}", doc.Status)
        End Sub "Main
    End Class</source>

Creating document with: Test Document
Implementing the Read Method for Printable
Implementing Zip
Document Status: -1

Public Sub aMethod() Implements Interface1.Method, Interface2.Method

<source lang="vbnet">Public Interface I1

   Sub Draw()

End Interface Public Interface I2

   Sub Draw()

End Interface Public Class Class1

   Implements I1, I2
   Public Sub foo() Implements I1.Draw, I2.Draw
   End Sub

End Class</source>

Reimplement interface

<source lang="vbnet">Class BaseClass

   Implements IFormattable
   Implements IComparable
   Public Value As String
   Public Overridable Overloads Function ToString(ByVal _
     Format As String, ByVal Provider As IFormatProvider) _
     As String Implements IFormattable.ToString
       ToString = Value
   End Function
   Public Overridable Overloads Function CompareTo(ByVal A _
     As Object) As Integer Implements IComparable.rupareTo
       If (Value = A.Value) Then
           CompareTo = 0
       ElseIf (Value < A.Value) Then
           CompareTo = -1
       Else
           CompareTo = 1
       End If
   End Function
   Public Sub New(ByVal Value As String)
       Me.Value = Value
   End Sub

End Class Class DerivedClass

   Inherits BaseClass
   Public Overrides Function ToString(ByVal _
     Format As String, ByVal Provider As IFormatProvider) _
     As String
       ToString = UCase(Value)
   End Function
   Public Sub New(ByVal Value As String)
       MyBase.New(Value)
   End Sub

End Class Module Module1

   Sub Main()
       Dim A As New BaseClass("Hello")
       Dim B As New DerivedClass("Hi")
       Console.WriteLine(A)
       Console.WriteLine(B)
       Console.WriteLine(A.rupareTo(B))
   End Sub

End Module</source>

Hello
HI
-1

Two classes implement one interface

<source lang="vbnet">public class Test

  public Shared Sub Main
       Dim rect As New Rectangle()
       Dim trap As New Trapezoid()
       rect.Draw()
       trap.Draw()
  End Sub

End class Public Interface IShape

   Function Draw() As String

End Interface Public Class Rectangle

   Implements IShape
   Public Function Draw() As String Implements IShape.Draw
       Return "Drawing Rectangle"
   End Function

End Class Public Class Trapezoid

   Implements IShape
   Public Function Draw() As String Implements IShape.Draw
       Return "Drawing Trapezoid"
   End Function

End Class</source>