C#-----事件委托EventHandler的定義與使用

     EventHandler表示將處理不包含事件數據的事件的方法

   1.聲明一個繼承EventArgs的子類，傳遞參數

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EventHandlerExample
{
    public class ClassInfoEventArgs:EventArgs
    {
        /// <summary>
        /// 班級所屬年級
        /// </summary>
        public string ClassGrade { get; set; }
        /// <summary>
        /// 班級名稱
        /// </summary>
        public string ClassName { get; set; }
        /// <summary>
        /// 構造方法
        /// </summary>
        /// <param name="ClassGrade"></param>
        /// <param name="ClassName"></param>
        public ClassInfoEventArgs(string ClassGrade, string ClassName)
        {
            this.ClassGrade = ClassGrade;
            this.ClassName = ClassName;
        }
    }
}

   2.聲明委托對象、執行方法，將方法綁定委托對象

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EventHandlerExample
{
    public class StudentInfo
    {
        /// <summary>
        /// 聲明委托對象
        /// </summary>
        public event EventHandler<ClassInfoEventArgs> showStudentInfo;

        public StudentInfo()
        {
            //綁定
            showStudentInfo += new EventHandler<ClassInfoEventArgs>(showStudentInfoMethod);
        }

        /// <summary>
        /// 聲明一個方法綁定委托
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="classInfoEvent"></param>
        public void showStudentInfoMethod(object sender, ClassInfoEventArgs classInfoEvent)
        {
            Console.WriteLine("我是" + classInfoEvent.ClassGrade + classInfoEvent.ClassName + "的學生");
        }

        /// <summary>
        /// 調用方法，開啟委托
        /// </summary>
        public void callShowStudentInfo(ClassInfoEventArgs classInfoEvent)
        {
            if (showStudentInfo!=null)
            {
                showStudentInfo(this, classInfoEvent);
            }
        }
    }
}

   3.開啟EventHandler委托

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EventHandlerExample
{
    class Program
    {
        static void Main(string[] args)
        {
            ClassInfoEventArgs classInfoEvent = new ClassInfoEventArgs("三年級", "二班");
            StudentInfo studentInfo = new StudentInfo();
            studentInfo.callShowStudentInfo(classInfoEvent);
        }       
    }
}