C#网络编程中常用特性介绍

特性一：委托

委托是C#语言中特有的概念，相当于C/C++中的函数指针，与C/C++中函数指针的不同之处是：委托是面向对象的、类型安全的和保险的，是引用类型。因此，对委托的使用要

“先定义、后声明，接着实例化、然后作为参数传递给方法，最后才能使用”。

1、定义委托使用关键字delegate:

delegate  void SomeDelegate(type1 para1,......typen paran);

2、声明委托：

SomeDelegate  d;

3、实例化委托：

d=new SomeDelegate(obj.InstanceMethod);

其中obj是对象，InstanceMethod是它的实例方法。

4、作为参数传递给方法

someMethod(d);

5、最后在此方法的实现代码中使用委托

private  void  someMethod(SomeDelegate  someDelegate)
{
   .....
   //使用委托
  someDelegate(arg1,arg2,....,argn);
  ...... 
}

通过委托SomeDelegate实现对方法InstanceMethod的调用，调用还必须有一个前提条件：方法InstanceMethod有参数且和定义SomeDelegate的参数一致，并且返回类型相同（本例中为void）。方法InstanceMethod的定义：

private  void  InstanceMethod(type1 para1,type2 para2,......,typen paran)
{
   //方法体
  .....
}

委托的实例化中的参数既可以是实例方法，也可以是静态方法。

使用委托实现“文字抄写员”的小程序，界面如下：

在下方文本框中编辑文字，勾选“书写到”组框中的“文本区1”和（或）“文本区2”复选框后单击“提交”按钮，程序会自动将文本框中的文字“抄写”到对应的用户勾选的文本区中去。

代码实现如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace DelegateDemo
{
    public partial class FrmMain : Form
    {
        public FrmMain()
        {
            InitializeComponent();
        }

        //1、定义委托
        private delegate void WriteToTextBox(string strTxt);
        //2、声明委托
        private WriteToTextBox writeToTextBox;

        /// <summary>
        /// 提交
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_OK_Click(object sender, EventArgs e)
        {
            if (chbOne.Checked)
            {
                gbJobOne.Text = "运行中......";
                gbJobOne.Refresh();
                txtJobOne.Clear();
                //3、实例化委托
                writeToTextBox = new WriteToTextBox(WriteTextBox1);
                //4、将委托作为方法的参数进行传递
                WriteText(writeToTextBox);
                gbJobOne.Text = "任务1完成";
            }
            if (chbTwo.Checked)
            {

                gbJobTwo.Text = "运行中......";
                gbJobTwo.Refresh();
                txtJobTwo.Clear();
                //3、实例化委托
                writeToTextBox = new WriteToTextBox(WriteTextBox2);
                //4、将委托作为方法的参数进行传递
                WriteText(writeToTextBox);
                gbJobTwo.Text = "任务2完成";
            }
        }

        private void WriteText(WriteToTextBox writeMethod)
        {
            string strData = this.txt_Input.Text;
            writeMethod(strData);
        }
        private void WriteTextBox1(string strTxt)
        {
            this.txtJobOne.Text = strTxt;
        }

        private void WriteTextBox2(string strTxt)
        {
            this.txtJobTwo.Text = strTxt;
        }

        /// <summary>
        /// 窗体加载事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void FrmMain_Load(object sender, EventArgs e)
        {
            //设置文本框获取焦点
            this.ActiveControl = this.txt_Input;
            //this.txt_Input.Focus();
        }
    }
}

特性2：多线程

多线程的具体介绍请参考博文：https://www.jb51.net/article/238731.htm

使用多线程实现上一节的程序，代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;//引入多线程的命名空间

namespace DelegateDemo
{
    public partial class FrmMain : Form
    {
        public FrmMain()
        {
            InitializeComponent();
        }

        //1、定义委托
        private delegate void WriteToTextBox(string strTxt);
        //2、声明委托
        private WriteToTextBox writeToTextBox;

        /// <summary>
        /// 提交
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_OK_Click(object sender, EventArgs e)
        {
           //创建线程1
            Thread thread1 = new Thread(new ThreadStart(ExecuteTsk1));
            //启动线程1
            thread1.Start();

            //创建线程2
            Thread thread2 = new Thread(new ThreadStart(ExecuteTsk2));
            //启动线程2
            thread2.Start();

        }

        private void ExecuteTsk1()
        {
            if (chbOne.Checked)
            {
                gbJobOne.Text = "运行中......";
                gbJobOne.Refresh();
                txtJobOne.Clear();
                //3、实例化委托
                writeToTextBox = new WriteToTextBox(WriteTextBox1);
                //4、将委托作为方法的参数进行传递
                WriteText(writeToTextBox);
                gbJobOne.Text = "任务1完成";
            }
        }

        private void ExecuteTsk2()
        {
            if (chbTwo.Checked)
            {

                gbJobTwo.Text = "运行中......";
                gbJobTwo.Refresh();
                txtJobTwo.Clear();
                //3、实例化委托
                writeToTextBox = new WriteToTextBox(WriteTextBox2);
                //4、将委托作为方法的参数进行传递
                WriteText(writeToTextBox);
                gbJobTwo.Text = "任务2完成";
            }
        }

        private void WriteText(WriteToTextBox writeMethod)
        {
            string strData = this.txt_Input.Text;
            writeMethod(strData);
        }
        private void WriteTextBox1(string strTxt)
        {
            this.txtJobOne.Text = strTxt;
        }

        private void WriteTextBox2(string strTxt)
        {
            this.txtJobTwo.Text = strTxt;
        }

        /// <summary>
        /// 窗体加载事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void FrmMain_Load(object sender, EventArgs e)
        {
            //设置文本框获取焦点
            this.ActiveControl = this.txt_Input;
            //允许跨线程调用
            Control.CheckForIllegalCrossThreadCalls = false;
        }
    }
}

特性3：C#方法回调

C#回调的具体介绍请参照博文：https://www.jb51.net/article/238731.htm#_label3

使用委托、多线程和C#的方法回调机制实现上一节的程序，代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;//引入多线程的命名空间

namespace DelegateDemo
{
    public partial class FrmMain : Form
    {
        public FrmMain()
        {
            InitializeComponent();
        }

        //1、定义委托
        private delegate void WriteToTextBox(string strTxt);
        //2、声明委托
        private WriteToTextBox writeToTextBox;

        //定义并声明操作文本区1的回调
        private delegate void WriteTxtJobOneCallBack(string strValue);
        WriteTxtJobOneCallBack writeTxtJobOneCallBack;

        //定义并声明操作文本区2的回调
        private delegate void WriteTxtJobTwoCallBack(string strValue);
        WriteTxtJobOneCallBack writeTxtJobTwoCallBack;

        //定义并声明操作"任务1"分组框的回调
        private delegate void ShowGroupOneCallBack(string strValue);
        ShowGroupOneCallBack showGroupOneCallBack;

        //定义并声明操作"任务2"分组框的回调
        private delegate void ShowGroupTwoCallBack(string strValue);
        ShowGroupOneCallBack showGroupTwoCallBack;

        /// <summary>
        /// 提交
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_OK_Click(object sender, EventArgs e)
        {
           //创建线程1
            Thread thread1 = new Thread(new ThreadStart(ExecuteTsk1));
            //启动线程1
            thread1.Start();

            //创建线程2
            Thread thread2 = new Thread(new ThreadStart(ExecuteTsk2));
            //启动线程2
            thread2.Start();

        }

        private void ExecuteTsk1()
        {
            if (chbOne.Checked)
            {
                //3、实例化委托
                writeToTextBox = new WriteToTextBox(WriteTextBox1);
                //4、将委托作为方法的参数进行传递
                WriteText(writeToTextBox);
                //使用回调
                this.gbJobOne.Invoke(showGroupOneCallBack, "任务1");
            }
        }

        private void ExecuteTsk2()
        {
            if (chbTwo.Checked)
            {
                //3、实例化委托
                writeToTextBox = new WriteToTextBox(WriteTextBox2);
                //4、将委托作为方法的参数进行传递
                WriteText(writeToTextBox);
                //使用回调
                this.gbJobTwo.Invoke(showGroupTwoCallBack, "任务2");
            }
        }

        /// <summary>
        /// 执行自定义委托
        /// </summary>
        /// <param name="writeMethod"></param>
        private void WriteText(WriteToTextBox writeMethod)
        {
            string strData = this.txt_Input.Text;
            writeMethod(strData);
        }

        /// <summary>
        /// 给文本区1赋值
        /// </summary>
        /// <param name="strTxt"></param>
        private void WriteTextBox1(string strTxt)
        {
            //使用回调
            this.txtJobOne.Invoke(writeTxtJobOneCallBack, strTxt);
        }

        /// <summary>
        /// 给文本区2赋值
        /// </summary>
        /// <param name="strTxt"></param>
        private void WriteTextBox2(string strTxt)
        {
            //使用回调
            this.txtJobTwo.Invoke(writeTxtJobTwoCallBack, strTxt);
        }

        /// <summary>
        /// 窗体加载事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void FrmMain_Load(object sender, EventArgs e)
        {
            //设置文本框获取焦点
            this.ActiveControl = this.txt_Input;

            //实例化回调
            writeTxtJobOneCallBack = new WriteTxtJobOneCallBack(WriteToTextJobOne);
            writeTxtJobTwoCallBack = new WriteTxtJobOneCallBack(WriteToTextJobTwo);
            showGroupOneCallBack = new ShowGroupOneCallBack(ShowGroupOne);
            showGroupTwoCallBack = new ShowGroupOneCallBack(ShowGroupTwo);

        }

        /// <summary>
        /// 操作文本区1的回调要执行的方法
        /// </summary>
        /// <param name="strValue"></param>
        private void WriteToTextJobOne(string strValue)
        {
            this.txtJobOne.Text = strValue;
        }

        /// <summary>
        /// 操作文本区2的回调要执行的方法
        /// </summary>
        /// <param name="strValue"></param>
        private void WriteToTextJobTwo(string strValue)
        {
            this.txtJobTwo.Text = strValue;
        }

        /// <summary>
        /// 操作"任务1"分组框的回调要执行的方法
        /// </summary>
        /// <param name="strValue"></param>
        private void ShowGroupOne(string strValue)
        {
            this.gbJobOne.Text = strValue;
        }

        /// <summary>
        /// 操作"任务2"分组框的回调要执行的方法
        /// </summary>
        /// <param name="strValue"></param>
        private void ShowGroupTwo(string strValue)
        {
            this.gbJobTwo.Text = strValue;
        }
    }
}

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