界面设定图：

此外，程序还包含一个Timer控件用于定时执行命令，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。

源代码：

Public Class monitor1

    Dim i As Integer = 0
    Dim a As String

    Private Sub Form1_Load(sender As System.Object,e As System.EventArgs) Handles MyBase.Load
        Timer1.Enabled = True
        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
    End Sub

    Private Sub Timer1_Tick(sender As System.Object,e As System.EventArgs) Handles Timer1.Tick      'Timer1空间的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 Label2.Text = "网络断开自动关机功能：已开启" Then      '如果自动关机功能已开启
                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
                If result2 = vbCancel Then
                    Process.Start(systemD & "\shutdown.exe","-a")     '如果用户在关机前点击了对话框的“取消”按钮，则取消自动关机
                    Label2.Text = "网络断开自动关机功能：未开启"
                End If
            End If
        End If

    End Sub

    Private Sub Button1_Click(sender As System.Object,e As System.EventArgs) Handles Button1.Click
        Dim result1 As String
        If Label2.Text = "网络断开自动关机功能：未开启" Then
            Label2.Text = "网络断开自动关机功能：已开启"
            result1 = MsgBox("自动关机功能已开启，是否让程序后台运行？",vbYesNoCancel)
            Select Case result1
                Case vbYes
                    Me.WindowState = FormWindowState.Minimized      '如果用户选“是”，则隐藏程序
                Case vbCancel
                    Label2.Text = "网络断开自动关机功能：未开启"    '如果用户选“取消”，则取消设定
            End Select
        Else
            Label2.Text = "网络断开自动关机功能：未开启"
        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
    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
End Class

程序在Windows7 +Visual Studio 2010 Express下编译通过

下载地址：http://115.com/file/dpi9m1x6#

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