此范例会以递归方式列举网络芳邻的网络资源，在此范例中会使用到 mpr.dll API 函式库的 WNetEnumResource、WNetOpenEnum、WNetCloseEnum 函式来进行网络芳邻的网络资源的列举动作。
TAPIMpr 类别为 mpr.dll API 函式库的操作类别
1: ''' <summary>
2: ''' 网络芳邻相关函式库(mpr.dll)。
3: ''' </summary>
4: Public NotInheritable Class TAPIMpr
5: Public Enum EResourceScope As Integer
6: ''' <summary>
7: ''' 正联机的资源。
8: ''' </summary>
9: RESOURCE_CONNECTED = &H1
10: ''' <summary>
11: ''' 网络上所有的资源。
12: ''' </summary>
13: RESOURCE_GLOBALNET = &H2
14: ''' <summary>
15: ''' 曾经联机的资源。
16: ''' </summary>
17: RESOURCE_REMEMBERED = &H3
18: End Enum
19:
20: Public Enum EResourceType As Integer
21: ''' <summary>
22: ''' 所有网络资源。
23: ''' </summary>
24: RESOURCETYPE_ANY = &H0
25: ''' <summary>
26: ''' 网络磁盘驱动器。
27: ''' </summary>
28: RESOURCETYPE_DISK = &H1
29: ''' <summary>
30: ''' 网络打印机。
31: ''' </summary>
32: RESOURCETYPE_PRINT = &H2
33: ''' <summary>
34: ''' 未知。
35: ''' </summary>
36: RESOURCETYPE_UNKNOWN = &HFFFFFFFF
37: End Enum
38:
39: Public Enum EResourceDisplayType As Integer
40: ''' <summary>
41: ''' 一般资源。
42: ''' </summary>
43: RESOURCEDISPLAYTYPE_GENERIC = 0
44: ''' <summary>
45: ''' 网域资源。
46: ''' </summary>
47: RESOURCEDISPLAYTYPE_DOMAIN = 1
48: ''' <summary>
49: ''' 服务器资源。
50: ''' </summary>
51: RESOURCEDISPLAYTYPE_SERVER = 2
52: ''' <summary>
53: ''' 共享资源。
54: ''' </summary>
55: RESOURCEDISPLAYTYPE_SHARE = 3
56: ''' <summary>
57: ''' 档案资源。
58: ''' </summary>
59: RESOURCEDISPLAYTYPE_FILE = 4
60: RESOURCEDISPLAYTYPE_GROUP = 5
61: RESOURCEDISPLAYTYPE_NETWORK = 6
62: RESOURCEDISPLAYTYPE_ROOT = 7
63: RESOURCEDISPLAYTYPE_SHAREADMIN = 8
64: RESOURCEDISPLAYTYPE_DIRECTORY = 9
65: RESOURCEDISPLAYTYPE_TREE = 10
66: RESOURCEDISPLAYTYPE_NDSCONTAINER = 11
67: End Enum
68:
69: Public Enum EResourceUsage As Integer
70: RESOURCEUSAGE_CONNECTABLE = &H1
71: RESOURCEUSAGE_CONTAINER = &H2
72: RESOURCEUSAGE_NOLOCALDEVICE = &H4
73: RESOURCEUSAGE_SIBLING = &H8
74: RESOURCEUSAGE_ATTACHED = &H10
75: RESOURCEUSAGE_ALL = (RESOURCEUSAGE_CONNECTABLE Or RESOURCEUSAGE_CONTAINER Or RESOURCEUSAGE_ATTACHED)
76: RESOURCEUSAGE_RESERVED = &H80000000
77: End Enum
78:
79: ''' <summary>
80: ''' 网络资源定义。
81: ''' </summary>
82: <StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> _
83: Public Class TNetResource
84: Public dwScope As EResourceScope
85: Public dwType As EResourceType
86: Public dwDisplayType As EResourceDisplayType
87: Public dwUsage As EResourceUsage
88: <MarshalAs(UnmanagedType.LPTStr)> _
89: Public LocalName As String
90: <MarshalAs(UnmanagedType.LPTStr)> _
91: Public RemoteName As String
92: <MarshalAs(UnmanagedType.LPTStr)> _
93: Public Comment As String
94: <MarshalAs(UnmanagedType.LPTStr)> _
95: Public Provider As String
96: End Class
97:
98: ''' <summary>
99: ''' 列举网络芳邻的网络资源。
100: ''' </summary>
101: ''' <param name="Handle">从 WNetOpenEnum 函数返回的一个句柄。</param>
102: ''' <param name="Count">最初设为要枚举的最大资源数量；或设为-1，表示枚举尽可能多的资源。一旦返回，就会设为实际枚举的资源数量。</param>
103: ''' <param name="NetResource">通常是一个字节缓冲区的首字节。该缓冲区装载了列举信息。</param>
104: ''' <param name="Size">缓冲区大小。</param>
105: <DllImport("mpr.dll", CharSet:=CharSet.Auto)> _
106: Public Shared Function WNetEnumResource(ByVal Handle As IntPtr, ByRef Count As Integer, ByVal NetResource As IntPtr, ByRef Size As Integer) As Integer
107: End Function
108:
109: ''' <summary>
110: ''' 启动对网络资源进行列举的过程。这个函数会返回由 WNetEnumResource 函数用于列举资源所用的一个句柄。
111: ''' </summary>
112: ''' <param name="Scope">要列举的资源范围。</param>
113: ''' <param name="Type">要列举的资源类型。</param>
114: ''' <param name="Usage">要列举的资源使用状况。</param>
115: ''' <param name="NetResource">网络资源定义。</param>
116: ''' <param name="Handle">传出一个句柄。该句柄由 WNetEnumResource 函数使用。必须用 WNetCloseEnum 函数将其清除。</param>
117: <DllImport("mpr.dll", CharSet:=CharSet.Auto)> _
118: Public Shared Function WNetOpenEnum(ByVal Scope As EResourceScope, ByVal Type As EResourceType, ByVal Usage As EResourceUsage, ByVal NetResource As TNetResource, <Out()> ByRef Handle As IntPtr) As Integer
119: End Function
120:
121: ''' <summary>
122: ''' 结束列举操作。
123: ''' </summary>
124: ''' <param name="Handle">由 WNetOpenEnum 函数返回的一个列举句柄。</param>
125: <DllImport("mpr.dll", CharSet:=CharSet.Auto)> _
126: Public Shared Function WNetCloseEnum(ByVal Handle As IntPtr) As Integer
127: End Function
128:
129: End Class
下列程序代码中的 NetEnumResource 为列举网络芳邻的网络资源的函式，NetEnumResourceCallback 为执行 NetEnumResource 方法的回呼函式。
1: ''' <summary>
2: ''' 执行 NetEnumResource 方法的回呼函式。
3: ''' </summary>
4: ''' <param name="NetResource">网络资源定义。</param>
5: ''' <param name="Cancel">是否取消列举动作。</param>
6: Public Delegate Sub NetEnumResourceCallback(ByVal NetResource As TAPIMpr.TNetResource, ByRef Cancel As Boolean)
7:
8: ''' <summary>
9: ''' 列举网络芳邻的网络资源。
10: ''' </summary>
11: ''' <param name="NetResource">网络资源定义。</param>
12: ''' <param name="CallBack">列举过程中的回呼函式。</param>
13: Public Shared Sub NetEnumResource(ByVal NetResource As TAPIMpr.TNetResource, ByVal CallBack As NetEnumResourceCallback)
14: Dim bCancel As Boolean
15: Dim iRet As Integer
16: Dim oHandle As IntPtr = New IntPtr()
17: Dim iEntries As Integer
18: Dim iBuffer As Integer = 16384
19: Dim oBuffer As IntPtr
20: Dim oNetResource As TAPIMpr.TNetResource
21: Dim iPtr As Int32
22: Dim N1 As Integer
23: Dim oStructure As Object
24:
25: bCancel = False
26: Try
27: iRet = TAPIMpr.WNetOpenEnum( _
28: TAPIMpr.EResourceScope.RESOURCE_GLOBALNET, _
29: TAPIMpr.EResourceType.RESOURCETYPE_ANY, _
30: TAPIMpr.EResourceUsage.RESOURCEUSAGE_ALL, NetResource, oHandle)
31: If iRet <> 0 Then Exit Sub
32:
33: oBuffer = Marshal.AllocHGlobal(iBuffer)
34: Do
35: iEntries = -1
36: iBuffer = 16384
37: iRet = TAPIMpr.WNetEnumResource(oHandle, iEntries, oBuffer, iBuffer)
38: If iRet <> 0 OrElse iEntries < 1 Then Exit Sub
39: iPtr = oBuffer.ToInt32
40: For N1 = 0 To iEntries - 1
41: oStructure = Marshal.PtrToStructure(CType(iPtr, IntPtr), GetType(TAPIMpr.TNetResource))
42: oNetResource = DirectCast(oStructure, TAPIMpr.TNetResource)
43:
44: '列举过程中的回呼函式
45: CallBack.Invoke(oNetResource, bCancel)
46: If bCancel = True Then Exit Do
47:
48: '若为 RESOURCEUSAGE_CONTAINER 则利用递归往下层列举网络资源
49: If (TAPIMpr.EResourceUsage.RESOURCEUSAGE_CONTAINER = _
50: (oNetResource.dwUsage And TAPIMpr.EResourceUsage.RESOURCEUSAGE_CONTAINER)) Then
51: NetEnumResource(oNetResource, CallBack)
52: End If
53: iPtr = iPtr + Marshal.SizeOf(oNetResource)
54: Next
55: Loop
56:
57: Marshal.FreeHGlobal(oBuffer)
58: TAPIMpr.WNetCloseEnum(oHandle)
59: Catch ex As Exception
60: End Try
61: End Sub
在窗体上放置一个 ListBox 控件来显示列举的网络资源，呼叫 NetEnumResource 函式来进行列举，呼叫 NetEnumResource 函式的自变量需传入事先定义好的 NetEnumResourceCallback 回呼函式；当列举的过程序，当找到网络资源时就会执行 NetEnumResourceCallback 函式，利用传入的 NetResource 自变量就可以依序列举网络资源。
1: ''' <summary>
2: ''' 执行 WNetEnumResource 方法的回呼函式。
3: ''' </summary>
4: ''' <param name="NetResource">网络资源定义。</param>
5: ''' <param name="Cancel">是否取消列举动作。</param>
6: Public Sub NetEnumResourceCallback(ByVal NetResource As TAPIMpr.TNetResource, ByRef Cancel As Boolean)
7: Dim sText As String
8:
9: sText = String.Format(" {0} : LocalName='{1}' RemoteName='{2}'", NetResource.dwDisplayType.ToString, NetResource.LocalName, NetResource.RemoteName)
10: ListBox1.Items.Add(sText)
11: Application.DoEvents()
12: End Sub
13:
14: Private Sub Button10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button10.Click
15: Me.Cursor = Cursors.WaitCursor
16: Try
17: ListBox1.Items.Clear()
18: TBMpr.NetEnumResource(Nothing, New NetEnumResourceCallback(AddressOf NetEnumResourceCallback))
19: MsgBox("执行完成!")
20: Finally
21: Me.Cursor = Cursors.Default
22: End Try
23: End Sub
