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vb功能实例介绍。详细、很好的实例说明。

<p>检测网络是否连通</p>
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<p>　　连通检测 </p>
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<p>　　许多应用程序常常需要在程序中直接进行联网操作，以便进行一些必要的处理（如在线注册和在线帮助等），这就要求我们在程序中建立某些连接。很多软件在不知用户是否联网的情况下就启动浏览器查找网址，结果只能查出一错误网页，既浪费用户时间又没有任何效果。如果应用程序在查找网页之前能自动判断用户是否已经联网，就会节约许多时间，提高程序运行效率。 </p>
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<p>　　下面是实现网络连通检测的VB 6代码： </p>
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<p>Private Sub Form_Load() </p>
<p>　If IsConnected = TRUE Then </p>
<p>　　MsgBox (“您已经连通了Internet!”) </p>
<p>　End If </p>
<p>　If IsConnected = FALSE Then </p>
<p>　　MsgBox (“您还没有连通 Internet!”) </p>
<p>　End If </p>
<p>End Sub </p>
<p></p>
<p>　 </p>
<p>Option Explicit </p>
<p>/＊有关的API声明和定义＊/ </p>
<p>Public Declare Function RasEnumConnections Lib “RasApi32.dll” Alias “RasEnumConnectionsA” (lpRasCon As Any, lpcb As Long, lpcConnections As Long) As Long </p>
<p>　 </p>
<p>Public Declare Function RasGetConnectStatus Lib “RasApi32.dll” Alias “RasGetConnectStatusA” (ByVal hRasCon As Long, lpStatus As Any) As Long </p>
<p></p>
<p>　 </p>
<p>/＊常数和变量的设定＊/ </p>
<p>Public Const RAS95_MaxEntryName = 256 </p>
<p>Public Const RAS95_MaxDeviceType = 16 </p>
<p>Public Const RAS95_MaxDeviceName = 32 </p>
<p>Public Type RASCONN95 </p>
<p>dwSize As Long </p>
<p>hRasCon As Long </p>
<p>szEntryName(RAS95_MaxEntryName) As Byte </p>
<p>szDeviceType(RAS95_MaxDeviceType) As Byte </p>
<p>szDeviceName(RAS95_MaxDeviceName) As Byte </p>
<p>End Type </p>
<p>Public Type RASCONNSTATUS95 </p>
<p>dwSize As Long </p>
<p>RasConnState As Long </p>
<p>dwError As Long </p>
<p>szDeviceType(RAS95_MaxDeviceType) As Byte </p>
<p>szDeviceName(RAS95_MaxDeviceName) As Byte </p>
<p>End Type </p>
<p>　 </p>
<p></p>
<p></p>
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<p>/＊函数IsConnected返回连通的状态，如果为True则表示已连通＊/ </p>
<p>Public Function IsConnected() As Boolean </p>
<p>　Dim TRasCon(255) As RASCONN95 </p>
<p>　Dim lg As Long </p>
<p>　Dim lpcon As Long </p>
<p>　Dim RetVal As Long </p>
<p>　Dim Tstatus As RASCONNSTATUS95 </p>
<p>　TRasCon(0).dwSize = 412 </p>
<p>　lg = 256 ＊ TRasCon(0).dwSize </p>
<p>　RetVal = RasEnumConnections(TRasCon(0), lg, lpcon) </p>
<p>　If RetVal <> 0 Then </p>
<p>　　MsgBox “错误” </p>
<p>　　Exit Function </p>
<p>　End If </p>
<p>　Tstatus.dwSize = 160 </p>
<p>　RetVal = RasGetConnectStatus(TRasCon(0) </p>
<p>.hRasCon,Tstatus) </p>
<p>　If Tstatus.RasConnState = ＆H2000 Then </p>
<p>　　IsConnected = TRUE </p>
<p>　Else </p>
<p>　　IsConnected = FALSE </p>
<p>　End If </p>
<p>End Function  </p>