委托

// Declare delegate -- defines required signature:
delegate double MathAction(double num);

class DelegateTest
{
    // Regular method that matches signature:
    static double Double(double input)
    {
        return input * 2;
    }

    static void Main()
    {
        // Instantiate delegate with named method:
        MathAction ma = Double;

        // Invoke delegate ma:
        double multByTwo = ma(4.5);
        Console.WriteLine("multByTwo: {0}", multByTwo);

        // Instantiate delegate with anonymous method:
        MathAction ma2 = delegate(double input)
        {
            return input * input;
        };

        double square = ma2(5);
        Console.WriteLine("square: {0}", square);

        // Instantiate delegate with lambda expression
        MathAction ma3 = s => s * s * s;
        double cube = ma3(4.375);

        Console.WriteLine("cube: {0}", cube);
    }
    // Output:
    // multByTwo: 9
    // square: 25
    // cube: 83.740234375
}