C#中的delegate委托类型基本学习教程

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

public delegate void Del(string message);

 // Create a method for a delegate.
public static void DelegateMethod(string message)
{
  System.Console.WriteLine(message);
}


 // Instantiate the delegate.
Del handler = DelegateMethod;

// Call the delegate.
handler("Hello World");

public void MethodWithCallback(int param1, int param2, Del callback)
{
  callback("The number is: " + (param1 + param2).ToString());
}

MethodWithCallback(1, 2, handler);

The number is: 3

public class MethodClass
{
  public void Method1(string message) { }
  public void Method2(string message) { }
}

MethodClass obj = new MethodClass();
Del d1 = obj.Method1;
Del d2 = obj.Method2;
Del d3 = DelegateMethod;

//Both types of assignment are valid.
Del allMethodsDelegate = d1 + d2;
allMethodsDelegate += d3;

//remove Method1
allMethodsDelegate -= d1;

// copy AllMethodsDelegate while removing d2
Del oneMethodDelegate = allMethodsDelegate - d2;

int invocationCount = d1.GetInvocationList().GetLength(0);

delegate void Delegate1();
delegate void Delegate2();

static void method(Delegate1 d, Delegate2 e, System.Delegate f)
{
  // Compile-time error.
  //Console.WriteLine(d == e);

  // OK at compile-time. False if the run-time type of f 
  // is not the same as that of d.
  System.Console.WriteLine(d == f);
}

// Declare a delegate:
delegate void Del(int x);

// Define a named method:
void DoWork(int k) { /* ... */ }

// Instantiate the delegate using the method as a parameter:
Del d = obj.DoWork;

// Declare a delegate
delegate void Del(int i, double j);

class MathClass
{
  static void Main()
  {
    MathClass m = new MathClass();

    // Delegate instantiation using "MultiplyNumbers"
    Del d = m.MultiplyNumbers;

    // Invoke the delegate object.
    System.Console.WriteLine("Invoking the delegate using 'MultiplyNumbers':");
    for (int i = 1; i <= 5; i++)
    {
      d(i, 2);
    }

    // Keep the console window open in debug mode.
    System.Console.WriteLine("Press any key to exit.");
    System.Console.ReadKey();
  }

  // Declare the associated method.
  void MultiplyNumbers(int m, double n)
  {
    System.Console.Write(m * n + " ");
  }
}

  Invoking the delegate using 'MultiplyNumbers':
  2 4 6 8 10

// Declare a delegate
delegate void Del();

class SampleClass
{
  public void InstanceMethod()
  {
    System.Console.WriteLine("A message from the instance method.");
  }

  static public void StaticMethod()
  {
    System.Console.WriteLine("A message from the static method.");
  }
}

class TestSampleClass
{
  static void Main()
  {
    SampleClass sc = new SampleClass();

    // Map the delegate to the instance method:
    Del d = sc.InstanceMethod;
    d();

    // Map to the static method:
    d = SampleClass.StaticMethod;
    d();
  }
}

  A message from the instance method.
  A message from the static method.