VB.Net Tutorial/Class Module/Delegate

Comparison method based on delegate

Module Module1
    Class Employee
        Public FirstNme As String
        Public LastName As String
        Public Title As String
        Public Salary As Double
        Public Sub New(ByVal LastName As String, ByVal FirstNme As String, _
          ByVal Title As String, ByVal Salary As Double)
            Me.FirstNme = FirstNme
            Me.LastName = LastName
            Me.Title = Title
            Me.Salary = Salary
        End Sub
    End Class
    Delegate Function Compare(ByVal A As Employee, ByVal B As Employee) As Boolean
    Dim CompareMethod As New Compare(AddressOf CompareTitle)
    Function CompareTitle(ByVal A As Employee, ByVal B As Employee) As Boolean
        If (A.Title < B.Title) Then
            CompareTitle = False
        Else
            CompareTitle = True
        End If
    End Function
    Function CompareLastName(ByVal A As Employee, ByVal B As Employee) As Boolean
        If (A.LastName < B.LastName) Then
            CompareLastName = False
        Else
            CompareLastName = True
        End If
    End Function
    Function CompareSalary(ByVal A As Employee, ByVal B As Employee) As Boolean
        If (A.Salary < B.Salary) Then
            CompareSalary = False
        Else
            CompareSalary = True
        End If
    End Function
    Public Sub SortList(ByVal Employeelist() As Employee)
        Dim I, J As Integer
        Dim Temp As Employee
        For I = 0 To Employeelist.Length - 2
            For J = I + 1 To Employeelist.Length - 1
                If (CompareMethod(Employeelist(I), Employeelist(J))) Then
                    Temp = Employeelist(I)
                    Employeelist(I) = Employeelist(J)
                    Employeelist(J) = Temp
                End If
            Next
        Next
    End Sub
    Sub Main()
        Dim EmployeeList(3) As Employee
        EmployeeList(0) = New Employee("A","Z", "W", 49.99)
        EmployeeList(1) = New Employee("Z","A", "J", 49.99)
        EmployeeList(2) = New Employee("B", "X", "K", 49.99)
        EmployeeList(3) = New Employee("P","O", "A", 39.99)
        SortList(EmployeeList)
        Console.WriteLine("By Title")
        Dim EmployeeEntry As Employee
        For Each EmployeeEntry In EmployeeList
            Console.WriteLine(EmployeeEntry.LastName & " " & EmployeeEntry.Title & " " & EmployeeEntry.Salary)
        Next
        Console.WriteLine("By LastName")
        CompareMethod = AddressOf CompareLastName
        SortList(EmployeeList)
        For Each EmployeeEntry In EmployeeList
            Console.WriteLine(EmployeeEntry.LastName & " " & EmployeeEntry.Title & " " & EmployeeEntry.Salary)
        Next
        Console.WriteLine("By Salary")
        CompareMethod = AddressOf CompareSalary
        SortList(EmployeeList)
        For Each EmployeeEntry In EmployeeList
            Console.WriteLine(EmployeeEntry.LastName & " " & EmployeeEntry.Title & " " & EmployeeEntry.Salary)
        Next
    End Sub
End Module

By Title
P A 39.99
Z J 49.99
B K 49.99
A W 49.99
By LastName
A W 49.99
B K 49.99
P A 39.99
Z J 49.99
By Salary
P A 39.99
Z J 49.99
B K 49.99
A W 49.99

Define a delegate to be a pointer to a subroutine that has a string parameter.

public class Test
   public Shared Sub Main
        Dim m_DisplayStringRoutine As StringDisplayerType
        m_DisplayStringRoutine = AddressOf ShowStringInMessageBox " ShowStringInOutputWindow
        m_DisplayStringRoutine("Hello world")
   End Sub
    Private Delegate Sub StringDisplayerType(ByVal str As String)
    Private Shared Sub ShowStringInOutputWindow(ByVal str As String)
        Console.WriteLine(str)
    End Sub
    Private Shared Sub ShowStringInMessageBox(ByVal str As String)
        Console.WriteLine("+++"+str)
        
    End Sub
End class

+++Hello world

Define delegate

public class Test
    Private Delegate Function NumEmployeesDelegate() As Integer
    Private Delegate Function GetNameDelegate() As String
   public Shared Sub Main
      Dim emp As New Employee()    
        Dim show_name As GetNameDelegate
        show_name = AddressOf emp.ToString
        Console.WriteLine(show_name())
      
   End Sub
End class

Public Class Employee
    Public Shared Function GetNumEmployees() As Integer
        Return 13
    End Function
    Public Overrides Function ToString() As String
        Return "Employee"
    End Function
End Class

Employee

Delegate Function

Module Module1
    Delegate Function Numbers(ByVal A As Double, ByVal B As Double) As Double
    Function SubtractNumbers(ByVal A As Double, ByVal B As Double) As Double
        SubtractNumbers = A - B
    End Function
    Function AddNumbers(ByVal A As Double, ByVal B As Double) As Double
        AddNumbers = A + B
    End Function
    Sub Main()
        Dim DoNumbers As New Numbers(AddressOf SubtractNumbers)
        Console.WriteLine(DoNumbers.Invoke(100, 50))
        DoNumbers = AddressOf AddNumbers
        Console.WriteLine(DoNumbers.Invoke(100, 50))
    End Sub
End Module

50
150

Math delegation

Imports System
Module Test
  Sub Main()
    Console.WriteLine("Enter Operation to Perform")
    PerformOp(New MathOperation(AddressOf Math.Sin))
    PerformOp(New MathOperation(AddressOf Math.Cos))
    PerformOp(New MathOperation(AddressOf Math.Tan))
  End Sub
   Delegate Function MathOperation(ByVal radians As Double) As Double
   Private Sub PerformOp(ByVal op As MathOperation)
     Dim angle As Double = 12
     Dim radians As Double
     radians = (angle / 360) * 2 * Math.PI
     Dim result As Double
     result = op.Invoke(radians)
     result = Math.Round(result, 4)
     Console.Writeline("Result = " & result.ToString())
  End Sub
End Module

Enter Operation to Perform
Result = 0.2079
Result = 0.9781
Result = 0.2126

Multiple Delegates

Module Module1
    Delegate Sub NotifyInfo()
    Dim ListOfDelegates(3) As NotifyInfo
    Sub Testing()
        Console.WriteLine("AAA")
    End Sub
    Sub Coding()
        Console.WriteLine("BBB")
    End Sub
    Sub Meeting()
        Console.WriteLine("CCC")
    End Sub
    Sub Main()
        ListOfDelegates(0) = New NotifyInfo(AddressOf Coding)
        ListOfDelegates(1) = New NotifyInfo(AddressOf Testing)
        ListOfDelegates(2) = New NotifyInfo(AddressOf Meeting)
        Dim NotifyAll As New NotifyInfo(AddressOf Coding)
        NotifyAll = NotifyInfo.rubine(ListOfDelegates)
        NotifyAll.Invoke()
    End Sub
End Module

BBB
AAA
CCC

Use AddressOf to assign function to a delegate

public class Test
    Private Delegate Function NumEmployeesDelegate() As Integer
    Private Delegate Function GetNameDelegate() As String
   public Shared Sub Main
      Dim emp As New Employee()    
        Dim show_num As NumEmployeesDelegate
        show_num = AddressOf Employee.GetNumEmployees
        Console.WriteLine(show_num().ToString)
      
   End Sub
End class

Public Class Employee
    Public Shared Function GetNumEmployees() As Integer
        Return 13
    End Function
    Public Overrides Function ToString() As String
        Return "Employee"
    End Function
End Class

13

Use Delegate Sub

Module Module1
    Delegate Sub StringMethod(ByVal S As String)
    Sub DisplayString(ByVal S As String)
        Console.WriteLine(S)
    End Sub
    Sub UpperString(ByVal S As String)
        Console.WriteLine(UCase(S))
    End Sub
    Sub Main()
        Dim MyMethod As New StringMethod(AddressOf DisplayString)
        MyMethod.Invoke("Visual Basic .Net Programming")
        MyMethod = AddressOf UpperString
        MyMethod.Invoke("Visual Basic .Net Programming")
    End Sub
End Module

Visual Basic .Net Programming
VISUAL BASIC .NET PROGRAMMING

Uses delegates to sort random numbers (ascending or descending)

Public Class Tester

   Private Shared Function SortAscending(ByVal element1 As Integer, _
      ByVal element2 As Integer) As Boolean
      Return element1 > element2
   End Function " SortAscending
   Private Shared Function SortDescending(ByVal element1 As Integer, _
      ByVal element2 As Integer) As Boolean
      Return element1 < element2
   End Function " SortDescending
   Public Shared Sub Main
      Dim mBubbleSort As New BubbleSort()
      Dim mElementArray As Integer() = New Integer(9) {}
      Dim randomNumber As Random = New Random()
      Dim i As Integer
      " create String with 10 random numbers
      For i = 0 To mElementArray.GetUpperBound(0)
         mElementArray(i) = randomNumber.Next(100)
         Console.WriteLine(mElementArray(i))
      Next
    
      mBubbleSort.SortArray(mElementArray, AddressOf SortAscending)
      For i = 0 To mElementArray.GetUpperBound(0)
         Console.Write(mElementArray(i) & " " )
      Next
      Console.WriteLine()
      mBubbleSort.SortArray(mElementArray, AddressOf SortDescending)
      For i = 0 To mElementArray.GetUpperBound(0)
         Console.Write(mElementArray(i) & " " )
      Next
   End Sub
End Class
Public Class BubbleSort
   Public Delegate Function Comparator( _
      ByVal element1 As Integer, _
      ByVal element2 As Integer) As Boolean
   Public Sub SortArray(ByVal array As Integer(), _
      ByVal Compare As Comparator)
      Dim i, pass As Integer
      For pass = 0 To array.GetUpperBound(0)
         For i = 0 To array.GetUpperBound(0) - 1
            If Compare(array(i), array(i + 1)) Then
               Swap(array(i), array(i + 1))
            End If
         Next " inner loop
      Next " outer loop
   End Sub " SortArray
   Private Sub Swap(ByRef firstElement As Integer, _
      ByRef secondElement As Integer)
      Dim hold As Integer
      hold = firstElement
      firstElement = secondElement
      secondElement = hold
   End Sub " Swap
End Class

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