程序可以监控网络连接状态，可以设定网络断开的话就自动关机或运行程序。
新浪博客：http://blog.sina.com.cn/s/blog_647ee5f70100wicy.html
更新 ：
2.细节调整
3.修复Bug
4.错误处理
界面图及控件命名如下：
此外，程序还包含两个Timer控件，Timer1用于定时执行命令，Timer2用于获取当前时间并显示；一个NotifyIcon控件用于显示托盘图标；一个ContextMenuStrip控件用于托盘图标的右键菜单；一个OpenFileDialog控件用于打开文件。
源代码：
Public Class Monitor1
Dim a As Boolean
Private Sub Form1_Load(sender As System.Object,e As System.EventArgs) Handles MyBase.Load
Label3.Text = "当前时间：" & My.Computer.Clock.LocalTime.ToLongTimeString '获取当前时间并显示
Timer1.Interval = My.Settings.Interval1 '从设置中获取保存的检测间隔
ComboBox1.SelectedIndex = 1 '令检测间隔选择框默认显示第二项
If My.Settings.LWS = 1 Then '初始化【开机启动】复选框状态
CheckBox3.Checked = True
Else
CheckBox3.Checked = False
End If
If My.Settings.SWR = 1 Then '获取【运行即监控】设置
Timer1.Enabled = True
CheckBox4.Checked = True
Button1.Text = "关闭监视"
Label2.Text = "监视功能状态：已开启"
Label2.ForeColor = Color.DarkGreen
Else
Timer1.Enabled = False
CheckBox4.Checked = False
Button1.Text = "开启监视"
Label2.Text = "监视功能状态：已关闭"
Label2.ForeColor = Color.DarkRed
End If
a = My.Computer.Network.Ping("8.8.8.8") '通过Ping 8.8.8.8来判断网络是否连通
If a = True Then
Label1.Text = "网络状态：网络已连接" '如果网络已连接，则显示
Light1.FillColor = Color.Green '同时将“指示灯”颜色更改为绿色
Light1.FillGradientColor = Color.LightGreen
NotifyIcon1.Text = "网络监视器" & Chr(13) & "网络状态：网络已连接"
Else
Label1.Text = "网络状态：网络未连接"
NotifyIcon1.Text = "网络监视器" & Chr(13) & "网络状态：网络未连接"
End If
NotifyIcon1.ContextMenuStrip = ContextMenuStrip1 '为托盘图标添加右键菜单
If My.Settings.FilePath1 = "" Then
TextBox1.Text = "请输入要运行的程序路径"
Else
TextBox1.Text = My.Settings.FilePath1
End If
End Sub
Private Sub Timer1_Tick(sender As System.Object,_
e As System.EventArgs) Handles Timer1.Tick 'Timer1控件的Tick间隔为20000毫秒
Dim result2 As String
a = My.Computer.Network.Ping("8.8.8.8")
If a = True Then
Label1.Text = "网络状态：网络已连接"
Light1.FillColor = Color.Green
Light1.FillGradientColor = Color.LightGreen
NotifyIcon1.Text = "网络监视器" & Chr(13) & "网络状态：网络已连接" '设置托盘图标的显示内容
Else
Label1.Text = "网络状态：网络未连接" '如果网络未连接，则显示
Light1.FillColor = Color.Red '同时更改“指示灯”颜色为红色
Light1.FillGradientColor = Color.Pink
NotifyIcon1.Text = "网络监视器" & Chr(13) & "网络状态：网络未连接"
If CheckBox1.Checked = True Then '如果勾选【网络断开自动关机】
Dim systemD As String
systemD = System.Environment.SystemDirectory
Process.Start(systemD & "\shutdown.exe","-s -t 60") '则执行关机命令，延迟60秒
Timer1.Enabled = False '令Timer1不可用，以阻止多次执行同一动作
result2 = MsgBox("网络已断开，计算机将在60秒内关闭",MsgBoxStyle.OkCancel) '弹出对话框提示计算机即将关闭
Me.ShowInTaskbar = True
If result2 = vbCancel Then
Process.Start(systemD & "\shutdown.exe","-a") '若用户在关机前点击对话框的“取消”按钮，则取消自动关机
CheckBox1.Checked = False
Timer1.Enabled = True
End If
Else
If CheckBox2.Checked = True And TextBox1.Text <> "" Then '如果勾选【网络断开运行程序】
Try
Process.Start(TextBox1.Text) '则运行程序
CheckBox2.Checked = False
Catch ex As Exception
MsgBox("发生错误，可能是文件不存在！",MsgBoxStyle.Exclamation)
End Try
End If
End If
End If
End Sub
Private Sub CheckBox1_CheckedChanged(sender As System.Object,e As System.EventArgs) Handles CheckBox1.CheckedChanged
If CheckBox1.Checked = True Then
CheckBox2.Enabled = False
Else
CheckBox2.Enabled = True
End If
End Sub
Private Sub CheckBox2_CheckedChanged(sender As System.Object,e As System.EventArgs) Handles CheckBox2.CheckedChanged
If CheckBox2.Checked = True Then '如果选择了第二个单选按钮
CheckBox1.Enabled = False '禁用另一功能
TextBox1.Enabled = True '启用文本框
If TextBox1.Text = "请输入要运行的程序路径" Then
TextBox1.Text = "" '清空文本框内容
End If
Button2.Enabled = True '启用【浏览】按钮
Button3.Enabled = True '启用【保存路径】按钮
Else
CheckBox1.Enabled = True
TextBox1.Enabled = False
If TextBox1.Text = "" Then
TextBox1.Text = "请输入要运行的程序路径"
End If
Button2.Enabled = False
Button3.Enabled = False
End If
End Sub
Private Sub CheckBox3_CheckedChanged(sender As System.Object,e As System.EventArgs) Handles CheckBox3.CheckedChanged
If CheckBox3.Checked = True Then
Try
My.Computer.Registry.SetValue("HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run",_
"NetworkMonitor",Application.ExecutablePath) '写入注册表
Catch ex As Exception
MsgBox("发生未知错误，错误代码：" & Err.Number) '其实几乎不可能发生错误
End Try
MsgBox("设置完毕,已启用开机自动运行",MsgBoxStyle.Information) '提示
My.Settings.LWS = 1 '保存设置
Else
Try
My.Computer.Registry.SetValue("HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run","")
Catch ex As Exception
MsgBox("发生错误，错误代码：" & Err.Number,MsgBoxStyle.Exclamation)
End Try
MsgBox("设置完毕，已禁止开机自动运行",MsgBoxStyle.Information)
My.Settings.LWS = 0
End If
End Sub
Private Sub CheckBox4_CheckedChanged(sender As System.Object,e As System.EventArgs) Handles CheckBox4.CheckedChanged
If CheckBox4.Checked = True Then
My.Settings.SWR = 1 '保存设置
Else
My.Settings.SWR = 0
End If
End Sub
Private Sub Button1_Click(sender As System.Object,e As System.EventArgs) Handles Button1.Click
If Button1.Text = "关闭监视" Then '点击【关闭监视】按钮
Timer1.Enabled = False '则禁用计时器，即停止监视功能
Label2.Text = "监视功能状态：已关闭" '显示状态
Label2.ForeColor = Color.DarkRed '修改字体颜色
Button1.Text = "开启监视" '修改按钮文本
Else
Timer1.Enabled = True
Label2.Text = "监视功能状态：已开启"
Label2.ForeColor = Color.DarkGreen
Button1.Text = "关闭监视"
End If
End Sub
Private Sub Button2_Click(sender As System.Object,e As System.EventArgs) Handles Button2.Click
Try
OpenFileDialog1.ShowDialog()
TextBox1.Text = OpenFileDialog1.FileName
Catch ex As Exception
MsgBox("发生错误",MsgBoxStyle.Exclamation)
End Try
End Sub
Private Sub Button3_Click(sender As System.Object,e As System.EventArgs) Handles Button3.Click
If TextBox1.Text <> "请请输入要运行的程序路径" And TextBox1.Text <> "" Then
My.Settings.FilePath1 = TextBox1.Text
Else
MsgBox("请输入正确的路径",MsgBoxStyle.Exclamation)
End If
End Sub
Private Sub Button4_Click(sender As System.Object,e As System.EventArgs) Handles Button4.Click
If Me.Width = 425 Then
Me.Width = 700 '展开【设置】部分
GroupBox2.Enabled = True '启用【设置】部分
Button4.Text = "设置 <<"
Else
Me.Width = 425
GroupBox2.Enabled = False
Button4.Text = "设置 >>"
End If
End Sub
Private Sub Button5_Click(sender As System.Object,e As System.EventArgs) Handles Button5.Click
Dim interval2 As Integer
If Button5.Text = "设置检测间隔" Then
Button5.Text = "保存"
ComboBox1.Enabled = True
Else
Select Case ComboBox1.Text
Case "10秒"
interval2 = 10000
Case "20秒（默认）"
interval2 = 20000
Case "30秒"
interval2 = 30000
Case "1分钟"
interval2 = 60000
Case "2分钟"
interval2 = 120000
Case "5分钟"
interval2 = 300000
Case "10分钟"
interval2 = 600000
Case "20分钟"
interval2 = 1200000
Case "30分钟"
interval2 = 1800000
End Select
My.Settings.Interval1 = interval2
Button5.Text = "设置检测间隔"
ComboBox1.Enabled = False
End If
End Sub
Private Sub NotifyIcon1_MouseDoubleClick(sender As System.Object,e As System.Windows.Forms.MouseEventArgs) Handles NotifyIcon1.MouseDoubleClick
Me.WindowState = FormWindowState.Normal '双击托盘图标，显示窗口
If Me.WindowState = FormWindowState.Minimized Then
Me.ShowInTaskbar = True
End If
End Sub
Private Sub monitor1_Resize(sender As Object,e As System.EventArgs) Handles Me.Resize
If Me.WindowState = FormWindowState.Minimized Then
Me.ShowInTaskbar = False '当程序最小化，则不在任务栏显示图标
End If
End Sub
Private Sub ShownHide1_Click(sender As System.Object,e As System.EventArgs) Handles ShownHide1.Click
If ShownHide1.Text = "隐藏窗口" Then
Me.WindowState = FormWindowState.Minimized
ShownHide1.Text = "显示窗口"
Else
Me.WindowState = FormWindowState.Normal
ShownHide1.Text = "隐藏窗口"
End If
End Sub
Private Sub Exit1_Click(sender As System.Object,e As System.EventArgs) Handles Exit1.Click
End
End Sub
Private Sub Timer2_Tick(sender As System.Object,e As System.EventArgs) Handles Timer2.Tick
Label3.Text = "当前时间：" & My.Computer.Clock.LocalTime.ToLongTimeString
End Sub
Private Sub LinkLabel1_LinkClicked(sender As System.Object,e As System.Windows.Forms.LinkLabelLinkClickedEventArgs) Handles LinkLabel1.LinkClicked
Try
System.Diagnostics.Process.Start("mailto:wangjingkaibear@live.cn")
Catch ex As Exception
MsgBox("没有关联的邮件程序",MsgBoxStyle.Exclamation)
End Try
End Sub
Private Sub OpenFileDialog1_FileOk(sender As System.Object,e As System.ComponentModel.CancelEventArgs) Handles OpenFileDialog1.FileOk
End Sub
End Class