今天重新学习了一下观察者模式，对我的思路产生了启发。进程监控程序之前写过几个，这回换一种思路，改用委托和事件来实现。我已经用序号将关键的几步标注，方便大家理顺思路。代码如下：
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace ProcessMonitor { public partial class ProcessMonitorForm : Form { public ProcessMonitorForm() { InitializeComponent(); //Add the processes into the combox. var processes = Process.GetProcesses(); foreach (var process in processes) { processComboBox.Items.Add(process.ProcessName.ToString()); } } //The method that starts the monitor. private void startButton_Click(object sender, EventArgs e) { //4.Register the monitor. ProcessExit += new ProcessMonitor(ProExit); //Start the check. CheckProcess(); } //The mothod that checks the process. private void CheckProcess() { bool flag = true; do { var processes = Process.GetProcesses(); int count = 0; foreach (var process in processes) { if (string.Compare(process.ProcessName, processComboBox.Text, true) == 0) { count++; } } if (count == 0) { //5.The event appears. ProcessExit(this, new EventArgs()); flag = false; } } while (flag); } //1.The delegate that monitor the process. public delegate void ProcessMonitor(object sender, EventArgs strEventArg); //2.The event that encapsulates the delegate. public event ProcessMonitor ProcessExit; //3.The method that the delegate calls. private void ProExit(object sender, EventArgs strEventArg) { MessageBox.Show("The target process has been dispeared."); } } }
为了不长篇累牍，效果只是简单实现，实际工作中可以随便扩展（选择进程，点击Start按钮进行监控。）：
目标程序消失后弹出提示：
再附上一个脱去委托和事件的版本，代码如下（实现效果相同）：
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace ProcessMonitor { public partial class ProcessMonitorForm : Form { public ProcessMonitorForm() { InitializeComponent(); //Add the processes into the combox. var processes = Process.GetProcesses(); foreach (var process in processes) { processComboBox.Items.Add(process.ProcessName.ToString()); } } //The method that starts the monitor. private void startButton_Click(object sender, EventArgs e) { //Start the check. CheckProcess(); } //The mothod that checks the process. private void CheckProcess() { bool flag = true; do { var processes = Process.GetProcesses(); int count = 0; foreach (var process in processes) { if (string.Compare(process.ProcessName, processComboBox.Text, true) == 0) { count++; } } if (count == 0) { ProExit(); flag = false; } } while (flag); } private void ProExit() { MessageBox.Show("The target process has been dispeared."); } } }
如果用Action内置委托类型来完成的话就更方便了，代码如下（已经用序号标注关键步骤）：
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace ProcessMonitor { public partial class ProcessMonitorForm : Form { public ProcessMonitorForm() { InitializeComponent(); //Add the processes into the combox. var processes = Process.GetProcesses(); foreach (var process in processes) { processComboBox.Items.Add(process.ProcessName.ToString()); } } //The method that starts the monitor. private void startButton_Click(object sender, EventArgs e) { //Start the check. CheckProcess(); } //The mothod that checks the process. private void CheckProcess() { //1.Define the action. Action<string> processExit = s => MessageBox.Show(s); bool flag = true; do { var processes = Process.GetProcesses(); int count = 0; foreach (var process in processes) { if (string.Compare(process.ProcessName, processComboBox.Text, true) == 0) { count++; } } if (count == 0) { //2.Active the action. processExit("The target process has been dispeared."); flag = false; } } while (flag); } } }
脱去委托和事件的版本代码量明显比用委托和事件的代码量少了，为什么我们还要选择用委托和事件来做这件事呢？到底什么情况下，更适合用委托和事件的方式来完成？书中说，委托可以提高方法扩展性，没错，是这样的，说白了就是因为更高级！个人意见哈，在代码量少，以后不需要扩展方法的情况下，用不着用委托和事件的方式去完成，直接调用方法就好了。如果我说错了，欢迎指正我。
利用C#6.0中的语法糖扩展方法来替代foreach循环，代码量将更少。代码如下：
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace ProcessMonitor { public partial class ProcessMonitorForm : Form { public ProcessMonitorForm() { InitializeComponent(); //Add the processes into the combox. var processes = Process.GetProcesses(); foreach (var process in processes) { processComboBox.Items.Add(process.ProcessName.ToString()); } } //The method that starts the monitor. private void startButton_Click(object sender, EventArgs e) { //Start the check. CheckProcess(); } //The mothod that checks the process. private void CheckProcess() { //1.Define the action. Action<string> processExit = s => MessageBox.Show(s); bool flag = true; do { var processes = Process.GetProcesses(); var countVar = processes.Where(i => i.ProcessName == processComboBox.Text); if (countVar.Count() == 0) { //2.Active the action. processExit("The target process has been dispeared."); flag = false; } } while (flag); } } }