C# 委托（开发者如何使用）

// Delegate declaration
public delegate void MyDelegate(string message);

class Program
{
    static void Main(string[] args)
    {
        // Instantiation
        MyDelegate myDelegate = DisplayMessage;

        // Invocation
        myDelegate("Hello, Delegates!");
    }

    // Method to be referenced
    static void DisplayMessage(string message)
    {
        Console.WriteLine(message);
    }
}

' Delegate declaration
Public Delegate Sub MyDelegate(ByVal message As String)

Friend Class Program
	Shared Sub Main(ByVal args() As String)
		' Instantiation
		Dim myDelegate As MyDelegate = AddressOf DisplayMessage

		' Invocation
		myDelegate("Hello, Delegates!")
	End Sub

	' Method to be referenced
	Private Shared Sub DisplayMessage(ByVal message As String)
		Console.WriteLine(message)
	End Sub
End Class

using System;

class Program
{
    static void Main(string[] args)
    {
        EventPublisher publisher = new EventPublisher();
        EventSubscriber subscriber = new EventSubscriber(publisher);

        publisher.SimulateEvent("Test Event");
    }
}

public class EventPublisher
{
    // Declare a delegate type
    public delegate void EventHandler(string eventName);

    // Create an instance of the delegate
    public event EventHandler EventOccurred;

    // Simulate an event
    public void SimulateEvent(string eventName)
    {
        // Invoke the delegate to notify subscribers
        EventOccurred?.Invoke(eventName);
    }
}

public class EventSubscriber
{
    public EventSubscriber(EventPublisher eventPublisher)
    {
        // Subscribe to the event using the delegate
        eventPublisher.EventOccurred += HandleEvent;
    }

    // Method to be invoked when the event occurs
    private void HandleEvent(string eventName)
    {
        Console.WriteLine($"Event handled: {eventName}");
    }
}

Imports System

Friend Class Program
	Shared Sub Main(ByVal args() As String)
		Dim publisher As New EventPublisher()
		Dim subscriber As New EventSubscriber(publisher)

		publisher.SimulateEvent("Test Event")
	End Sub
End Class

Public Class EventPublisher
	' Declare a delegate type
	Public Delegate Sub EventHandler(ByVal eventName As String)

	' Create an instance of the delegate
	Public Event EventOccurred As EventHandler

	' Simulate an event
	Public Sub SimulateEvent(ByVal eventName As String)
		' Invoke the delegate to notify subscribers
		RaiseEvent EventOccurred(eventName)
	End Sub
End Class

Public Class EventSubscriber
	Public Sub New(ByVal eventPublisher As EventPublisher)
		' Subscribe to the event using the delegate
		AddHandler eventPublisher.EventOccurred, AddressOf HandleEvent
	End Sub

	' Method to be invoked when the event occurs
	Private Sub HandleEvent(ByVal eventName As String)
		Console.WriteLine($"Event handled: {eventName}")
	End Sub
End Class

public delegate int MyDelegate(int x, int y);

public class Calculator
{
    public int PerformOperation(MyDelegate operation, int operand1, int operand2)
    {
        // Execute the operation method reference through the passed delegate
        return operation(operand1, operand2);
    }
}

// Usage
var calculator = new Calculator();
int result = calculator.PerformOperation((x, y) => x + y, 5, 3); // Adds 5 and 3
Console.WriteLine(result); // Outputs: 8

Public Delegate Function MyDelegate(ByVal x As Integer, ByVal y As Integer) As Integer

Public Class Calculator
	Public Function PerformOperation(ByVal operation As MyDelegate, ByVal operand1 As Integer, ByVal operand2 As Integer) As Integer
		' Execute the operation method reference through the passed delegate
		Return operation(operand1, operand2)
	End Function
End Class

' Usage
Private calculator = New Calculator()
Private result As Integer = calculator.PerformOperation(Function(x, y) x + y, 5, 3) ' Adds 5 and 3
Console.WriteLine(result) ' Outputs: 8