委托使用方法

原来是想写一篇关于委托的博客的，但是看了http://www.tracefact.net/tech/009.html关于C#委托的博客，不想写了

怎么写都不会有人家的好。

一、将方法作为参数传递

https://docs.microsoft.com/zh-cn/dotnet/csharp/tour-of-csharp/delegates

委托类型表示对具有特定参数列表和返回类型的方法的引用。 通过委托，可以将方法视为可分配给变量并可作为参数传递的实体。 委托类似于其他一些语言中的函数指针概念，但与函数指针不同的是，委托不仅面向对象，还类型安全。

using System;
delegate double Function(double x);
class Multiplier
{
    double factor;
    public Multiplier(double factor) 
    {
        this.factor = factor;
    }
    public double Multiply(double x) 
    {
        return x * factor;
    }
}
class DelegateExample
{
    static double Square(double x) 
    {
        return x * x;
    }
    static double[] Apply(double[] a, Function f) 
    {
        double[] result = new double[a.Length];
        for (int i = 0; i < a.Length; i++) result[i] = f(a[i]);
        return result;
    }
    static void Main() 
    {
        double[] a = {0.0, 0.5, 1.0};
        double[] squares = Apply(a, Square);
        double[] sines = Apply(a, Math.Sin);
        Multiplier m = new Multiplier(2.0);
        double[] doubles =  Apply(a, m.Multiply);
    }
}

二、调用事件

是带event关键字的委托实例

访问修饰符 event 委托名 事件名；

 public partial class FormMeasureResult : Form
    {
        //委托
        public delegate void FormClosedEventHandler();
        public event FormClosedEventHandler frmClosed = null;

        public FormMeasureResult()
        {
            InitializeComponent();
        }

        private void FormMeasureResult_FormClosed(object sender, FormClosedEventArgs e)
        {
            if (frmClosed != null)
            {
                frmClosed();
            }
        }
    }


 private void frmMeasureResult_frmColsed()  //FormColsed事件
        {
            //清空线对象
            if (pNewLineFeedback != null)
            {
                pNewLineFeedback.Stop();
                pNewLineFeedback = null;
            }
            //清空面对象
            if (pNewPolygonFeedback != null)
            {
                pNewPolygonFeedback.Stop();
                pNewPolygonFeedback = null;
                pAreaPointCol.RemovePoints(0, pAreaPointCol.PointCount); //清空点集中所有点
            }
            //清空量算画的线、面对象
            axMapControl1.ActiveView.PartialRefresh(esriViewDrawPhase.esriViewForeground, null, null);
            //结束量算功能
            pMouseOperate = string.Empty;
            axMapControl1.MousePointer = esriControlsMousePointer.esriPointerDefault;
        }