El documento contiene varios trucos y métodos para realizar tareas comunes en Visual Basic, como hacer que una ventana siempre sea visible, simular clics de ratón, copiar tablas entre bases de datos, reproducir sonido, controlar el volumen y detectar si hay conexión a Internet.

1. Trucos de Visual Basic
¿Como hacer una ventana siempre visible?
Declare Function SetWindowPos& Lib "user32" (ByVal hwnd As Long, ByVal _
hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long,_
ByVal cy As Long, ByVal wFlags As Long)
Public Const HWND_TOPMOST& = -1
Public Const SWP_NOMOVE& = &H2
Public Const SWP_NOSIZE& = &H1
Const FLAGS = SWP_NOMOVE Or SWP_NOSIZE
Public Sub ShowHoldForm(Ventana As Form)
Dim Success
'**** Para las ventanitas que quedan por encima de las demás, ****
Success = SetWindowPos(Ventana.hwnd, HWND_TOPMOST, 0, 0, 0, 0,
FLAGS)
End Sub
'-----------------------------
ShowHoldForm Form1
¿Cómo situar el puntero del ratón en el centro de un botón y
luego "provocar" la pulsación del mismo?
'------En un módulo
Const WM_LBUTTONDOWN = &H201
Const WM_LBUTTONUP = &H202
Private Declare Function PostMessageBynum Lib "user32" Alias "PostMessageA"
_
(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long,
ByVal lParam _
As Long) As Long 'enviar mensajes al control
Private Declare Function SetCursorPos Lib "user32" (ByVal X As Long, ByVal _
Y As Long) As Long 'posicionar el puntero del ratón
Private Declare Function GetWindowRect Lib "user32" (ByVal hwnd As Long, _
lpRect As RECT) As Long 'obtener la posición del control
Private Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
'----- ahora el proceso :
Dim l As Long, PosX As Long, PosY As Long, PosXY As Long
Dim lpRect As RECT

2. 'conocer las posición del botón relativa a la pantalla, en pixels
l = GetWindowRect(Command1.hwnd, lpRect)
'colocar el ratón sobre el centro del botón
PosX = lpRect.Left + ((lpRect.Right - lpRect.Left) / 2)
PosY = lpRect.Top + ((lpRect.Bottom - lpRect.Top) / 2)
l = SetCursorPos(PosX, PosY)
'obtener la posicion del centro del control relativa al propio control,
'en pixels
'no es obligatorio, es para que las coordenadas recibidas en el mousedown
'del control sean coherentes
'la posicion y va en la palabra alta y la x en la baja
PosXY = (PosY - lpRect.Top) * 65536 + (PosX - lpRect.Left)
'simular el click del ratón
l = PostMessageBynum(Command1.hwnd, WM_LBUTTONDOWN, 0&, PosXY)
l = PostMessageBynum(Command1.hwnd, WM_LBUTTONUP, 0&, PosXY)
¿Como deshabilitar el CTRL+ALT+DEL
Start a new Standard EXE project. Form1 is created by default.
Add two CommandButton controls (Command1 and Command2) to Form1.
Add the following code to Form1's General Declarations section:
'-----------------------------
Private Const SPI_SCREENSAVERRUNNING = 97&
Private Declare Function SystemParametersInfo Lib "User32" _
Alias "SystemParametersInfoA" _
(ByVal uAction As Long, _
ByVal uParam As Long, _
lpvParam As Any, _
ByVal fuWinIni As Long) As Long
Private Sub Form_Load()
Command1.Caption = "Disabled"
Command2.Caption = "Enabled"
End Sub
Private Sub Form_Unload(Cancel As Integer)
'Re-enable CTRL+ALT+DEL and ALT+TAB before the program 'terminates.
Command2_Click
End Sub
Private Sub Command1_Click()
Dim lngRet As Long
Dim blnOld As Boolean
lngRet = SystemParametersInfo(SPI_SCREENSAVERRUNNING, True, _
blnOld, 0&)
End Sub

3. Private Sub Command2_Click()
Dim lngRet As Long
Dim blnOld As Boolean
lngRet = SystemParametersInfo(SPI_SCREENSAVERRUNNING, False, _
blnOld, 0&)
End Sub
'Press the F5 key to run the program, and click the "Disabled"
'CommandButton. CTRL+ALT+DEL and ALT+TAB are disabled. Click the
'"Enabled" CommandButton to enable CTRL+ALT+DEL and ALT+TAB again.
Saber si el programa ya se esta ejecutando
if app.previnstance then msgbox "Ya se esta ejecutando una instancia de este
programa"
¿Como copiar todas las tablas de una base de datos en una
destino?
'---Esta rutina sirve para copiar todas las tablas de una base de datos en una
destino.
'Si las tablas ya existian en la base de datos de eliminan y se vuelven a crear con
'la misma estructura que tuvieran en origen
'Las tablas de la base destino que no se encuentren en origen no se modifican.
'Si el parametro boCopiarDatos es true (valor por defecto) ademas de
'estructura se copian los datos de las tablas.
Sub CopiaTablas(strOrigen As String, strDestino As String, Optional
boCopiarDatos As Boolean = True)
Dim dbOrigen As Database, dbDestino As Database
Dim tdOrigen As TableDef, tdDestino As TableDef
Dim fdOrigen As Field, fdDestino As Field
Dim idOrigen As Index, idDestino As Index
Dim prOrigen As Property, prDestino As Properties
Dim i As Long
Screen.MousePointer = vbHourglass
'---abrir origen y destino
Set dbOrigen = OpenDatabase(strOrigen, False)
Set dbDestino = OpenDatabase(strDestino, True)
'---hay propiedades que no se pueden copiar como el value de los campos
On Error Resume Next
'---para cada tabla de origen
For Each tdOrigen In dbOrigen.TableDefs
If (tdOrigen.Attributes And (dbSystemObject Or dbHiddenObject))
'---si la tabla no es del sistema
'---mirar si existe la tabla en destino
For Each tdDestino In dbDestino.TableDefs

4. If tdDestino.Name = tdOrigen.Name Then
'---si existe la borro
dbDestino.TableDefs.Delete tdDestino.Name
Exit For
End If
Next
'---creo la tabla en el destino
Set tdDestino = dbDestino.CreateTableDef(tdOrigen.Name, _
tdOrigen.Attributes, tdOrigen.SourceTableName, tdOrigen.Connect)
'---le anado los campos
For Each fdOrigen In tdOrigen.Fields
Set fdDestino = tdDestino.CreateField(fdOrigen.Name, _
fdOrigen.Type, fdOrigen.Size)
'---copio las propiedades del campo
For Each prOrigen In fdOrigen.Properties
fdDestino.Properties(prOrigen.Name) =_
fdOrigen.Properties(prOrigen.Name)
Next
tdDestino.Fields.Append fdDestino
Next
'---le anado los indices
For Each idOrigen In tdOrigen.Indexes
Set idDestino = tdDestino.CreateIndex(idOrigen.Name)
'---anado los campos al indice
For Each fdOrigen In idOrigen.Fields
Set fdDestino = idDestino.CreateField(fdOrigen.Name
idDestino.Fields.Append fdDestino
Next
'---copio las propiedades del indice
For Each prOrigen In idDestino.Properties
idDestino.Properties(prOrigen.Name) =
idOrigen.Properties(prOrigen.Name)
Next
tdDestino.Indexes.Append idDestino
Next
dbDestino.TableDefs.Append tdDestino
'---copio los datos de la tabla, si se solicito
If boCopiarDatos Then dbOrigen.Execute ("INSERT INTO " + _
tdDestino.Name + " IN '" + strDestino + "' SELECT * FROM " + tdDesti
End If
Next
'---cerrar origen y destino
dbOrigen.Close
dbDestino.Close
Set dbOrigen = Nothing: Set dbDestino = Nothing
Set tdOrigen = Nothing: Set tdDestino = Nothing
Set fdOrigen = Nothing: Set fdDestino = Nothing

5. Set idOrigen = Nothing: Set idDestino = Nothing
Set prOrigen = Nothing: Set prDestino = Nothing
Screen.MousePointer = vbDefault
End Sub
Esto soluciona lo de las búsquedas en los combos y no importa que tantos
registros tenga.
' para la autobúsqueda en los combos
Public Const CB_ERR = -1
Public Const CB_FINDSTRING = &H14C
Public Const CB_FINDSTRINGEXACT = &H158
Public Const CB_GETITEMDATA = &H150
Declare Function SendMessage Lib "User32" Alias "SendMessageA" (ByVal
hWndAs Long, ByVal wMsg As Long, ByVal wParam As Long, lparam As Any) As
Long
'--- luego en el modulo hagan esta subrutina:
Public Sub AutoMatch(cbo As ComboBox, KeyAscii As Integer)
Dim sBuffer As String
Dim lRetVal As Longs
Buffer = Left(cbo.Text, cbo.SelStart) & Chr(KeyAscii)
lRetVal = SendMessage((cbo.hWnd), CB_FINDSTRING, -1, ByVal sBuffer)
If lRetVal <> CB_ERR Then
cbo.ListIndex = lRetVal
cbo.Text = cbo.List(lRetVal)
cbo.SelStart = Len(sBuffer)
cbo.SelLength = Len(cbo.Text)
KeyAscii = 0
End If
End Sub
'----por ultimo en el combo con propiedad Style = 0 para que permita
escribir,escriben en el evento keypress lo siguiente:
Private Sub Combo2_KeyPress(KeyAscii As Integer)
AutoMatch Combo2, KeyAscii
End Sub
¿Como añadir sonido a un programa?
'*** En un módulo:
Public Declare Function sndPlaySound Lib "winmm.dll" _
Alias "sndPlaySoundA" (ByVal lpszSoundName As String, _
ByVal uFlags As Long) As Long
Public Const SND_LOOP = &H8
Public Const SND_NODEFAULT = &H2
Public Const SND_SYNC = &H0
Public Const SND_ASYNC = &H1

6. Public Function PlaySound (FileName As String, F As Long) As Long
PlaySound = sndPlaySound (FileName, F)
End Function
'***Y para llamarla:
PlaySound "C:WindowsMediaDing.wav", SND_ASYNC ' por ejemplo
¿Como controlar el volumen?
'(archivo MMSYSTEM.DLL para 16bits y WINMM.DLL para 32)
Declare Function waveOutGetVolume Lib "WINMM" (ByVal udeviceid As Integer,
lpdwvolume As Long) As Integer
Declare Function waveOutSetVolume Lib "WINMM" (ByVal udeviceid As Integer,
ByVal dwVolume As Long) As Integer
Declare Function midiOutSetVolume Lib "WINMM" (ByVal udeviceid As Integer,
ByVal dwVolume As Long) As Integer
Declare Function midiOutGetVolume Lib "WINMM" (ByVal udeviceid As Integer,
lpdwvolume As Long) As Integer
Declare Function auxOutGetVolume Lib "WINMM" (ByVal udeviceid As Integer,
lpdwvolume As Long) As Integer
Declare Function auxOutSetVolume Lib "WINMM" (ByVal udeviceid As Integer,
ByVal dwVolume As Long) As Integer
Imprimir un FORM
Printer.PrintForm
Imprimir un Gráfico
Clipboard.Clear
MSChart1.EditCopy 'Este pudiera ser tu objeto grafico
Printer.Print ""
Printer.PaintPicture
Clipboard.GetData(), 0, 0
Printer.EndDoc
¿Cómo registrar un control?
Ejecutar "REGSVR32 control.ocx"
Esta es la forma de registrarlos manualmente (puede ser OCX, DLL, etc)
¿Cómo reiniciar Windows?
'------------Declarar esta funcion en un modulo...
Declare Function ExitWindowsEx& Lib "user32" (ByVal uFlags&, ByVal
dwReserved&)
Public Const EWX_LOGOFF = 0
Public Const EWX_SHUTDOWN = 1
Public Const EWX_REBOOT = 2
Public Const EWX_FORCE = 4
'-----------------------
lresult = ExitWindowsEx(EWX_REBOOT, 0&) '---- Reinicia el sistema

7. lresult = ExitWindowsEx(EWX_SHUTDOWN, 0&) '---- Apaga el sistema
¿Como cambiar la imagen del escritorio?
Private Declare Function SystemParametersInfo Lib "user32" Alias _
"SystemParametersInfoA" _
(ByVal uAction As Long, ByVal uParam As Long, _
ByVal lpvParam As String, ByVal fuWinIni As Long) As Long
Const SPIF_UPDATEINIFILE = &H1
Const SPI_SETDESKWALLPAPER = 20
Const SPI_SETDESKPATTERN = 21
Const SPIF_SENDWININICHANGE = &H2
Private N As Long
N = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0&,_
"c:MiDirectorioMiFichero.bmp", SPIF_SENDWININICHANGE Or
SPIF_UPDATEINIFILE)
¿Como detectar si estoy conectado a Internet?
***************************************************************************
' Declaraciones de la API
'***************************************************************************
Option Explicit
Public Declare Function RasEnumConnections Lib "RasApi32.dll" Alias
"RasEnumConnectionsA"_
(lpRasCon As Any, lpcb As Long, lpcConnections As Long) As Long
Public Declare Function RasGetConnectStatus Lib "RasApi32.dll" Alias
"RasGetConnectStatusA"_
(ByVal hRasCon As Long, lpStatus As Any) As Long
Public Const RAS95_MaxEntryName = 256
Public Const RAS95_MaxDeviceType = 16
Public Const RAS95_MaxDeviceName = 32
Public Type RASCONN95
dwSize As Long
hRasCon As Long
szEntryName(RAS95_MaxEntryName) As Byte
szDeviceType(RAS95_MaxDeviceType) As Byte
szDeviceName(RAS95_MaxDeviceName) As Byte
End Type
Public Type RASCONNSTATUS95
dwSize As Long
RasConnState As Long

8. dwError As Long
szDeviceType(RAS95_MaxDeviceType) As Byte
szDeviceName(RAS95_MaxDeviceName) As Byte
End Type
'***************************************************************************
' DEVUELVE TRUE EN CASO DE ESTAR CONECTADO
' FALSE EN CASO CONTRARIO
'***************************************************************************
Public Function IsConnected() As Boolean
Dim TRasCon(255) As RASCONN95
Dim lg As Long
Dim lpcon As Long
Dim RetVal As Long
Dim Tstatus As RASCONNSTATUS95
TRasCon(0).dwSize = 412
lg = 256 * TRasCon(0).dwSize
RetVal = RasEnumConnections(TRasCon(0), lg, lpcon)
If RetVal <> 0 Then
MsgBox "ERROR"
Exit Function
End If
Tstatus.dwSize = 160
RetVal = RasGetConnectStatus(TRasCon(0).hRasCon, Tstatus)
If Tstatus.RasConnState = &H2000 Then
IsConnected = True
Else
IsConnected = False
End If
End Function
Desconectarse de Internet usando VB
'***Declarar en un módulo
Public Const RAS_MAXENTRYNAME As Integer = 256
Public Const RAS_MAXDEVICETYPE As Integer = 16
Public Const RAS_MAXDEVICENAME As Integer = 128
Public Const RAS_RASCONNSIZE As Integer = 412
Public Const ERR_SUCCESS As Integer = 0
Public Type RasEntryName
dwSize As Long

9. szEntryName(RAS_MAXENTRYNAME) As Byte
End Type
Public Type RasConn
dwSize As Long
hRasConn As Long
szEntryName(RAS_MAXENTRYNAME) As Byte
szDeviceType(RAS_MAXDEVICETYPE) As Byte
szDeviceName(RAS_MAXDEVICENAME) As Byte
End Type
Public Declare Function RasEnumConnections Lib _
"rasapi32.dll" Alias "RasEnumConnectionsA" (lpRasConn As Any, lpcb As Long, _
lpcConnections As Long) As Long
Public Declare Function RasHangUp Lib "rasapi32.dll" Alias _
"RasHangUpA" (ByVal hRasConn As Long) As Long
Public gstrISPName As String
Public ReturnCode As Long
'******Añadimos estas dos funciones :
Public Sub HangUp()
Dim i As Long
Dim lpRasConn(255) As RasConn
Dim lpcb As Long
Dim lpcConnections As Long
Dim hRasConn As Long
lpRasConn(0).dwSize = RAS_RASCONNSIZE
lpcb = RAS_MAXENTRYNAME * lpRasConn(0).dwSize
lpcConnections = 0
ReturnCode = RasEnumConnections( lpRasConn(0), lpcb, lpcConnections)
If ReturnCode = ERROR_SUCCESS Then
For i = 0 To lpcConnections - 1
If Trim(ByteToString(lpRasConn(i).szEntryName)) = Trim(gstrISPName)
Then
hRasConn = lpRasConn(i).hRasConn
ReturnCode = RasHangUp(ByVal hRasConn)
End If
Next i
End If
End Sub
Public Function ByteToString(bytString() As Byte) As String
Dim i As Integer
ByteToString = ""
i = 0
While bytString(i) = 0&
ByteToString = ByteToString & Chr(bytString(i))
i = i + 1
Wend
End Function

10. '***** Y para desconectar debemos hacer sólo :
Call HangUp
¿Como activar el salvapantallas desde VB?
Private Declare Function SendMessage Lib "user32" Alias _
"SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
ByVal wParam As Long, lParam As Long) As Long
Private Sub Command1_Click()
Call SendMessage(Me.hwnd, &H112, &HF140, 0&)
End Sub
¿Alinear los iconos del escritorio?
'************************************************************
' Declaraciones de la API para alinear los iconos
************************************************************
Private Declare Function GetWindow Lib "user32"_
(ByVal hwnd As Long, ByVal wCmd As Long) As Long
Private Declare Function SendMessage Lib "user32"_
Alias "SendMessageA" (ByVal hwnd As Long,_
ByVal wMsg As Long, ByVal wParam As Long, lParam As Long) As Long
Private Declare Function FindWindow Lib "user32" _
Alias "FindWindowA" (ByVal lpClassName As String, _
ByVal lpWindowName As String) As Long
Private Const GW_CHILD = 5
Private Const LVA_ALIGNLEFT = &H1
Private Const LVM_ARRANGE = &H1016
'************************************************************
' Alinear los iconos del escritorio
'************************************************************
Las instrucciones para alinear los iconos con
Dim hWnd1 As Long
Dim hWnd2 As Long
Dim Ret As Long
hWnd1 = FindWindow("Progman", vbNullString)
hWnd2 = GetWindow(hWnd1, GW_CHILD)
hWnd1 = GetWindow(hWnd2, GW_CHILD)
Ret = SendMessage(hWnd1, LVM_ARRANGE, LVA_ALIGNLEFT, 0)
¿Como asociar un fichero a un programa determinado?
'************************************************************
'Windows API/Global Declarations for :AssociateFileType
'************************************************************
Declare Function RegCreateKey& Lib "advapi32.DLL" Alias "_
RegCreateKeyA" (ByVal hKey&, ByVal lpszSubKey$, lphKey&)

11. Declare Function RegSetValue& Lib "advapi32.DLL" _
Alias "RegSetValueA" (ByVal hKey&, ByVal lpszSubKey$, _
ByVal fdwType&, ByVal lpszValue$, ByVal dwLength&)
' Return codes from Registration functions.
Public Const ERROR_SUCCESS = 0&
Public Const ERROR_BADDB = 1&
Public Const ERROR_BADKEY = 2&
Public Const ERROR_CANTOPEN = 3&
Public Const ERROR_CANTREAD = 4&
Public Const ERROR_CANTWRITE = 5&
Public Const ERROR_OUTOFMEMORY = 6&
Public Const ERROR_INVALID_PARAMETER = 7&
Public Const ERROR_ACCESS_DENIED = 8&
Global Const HKEY_CLASSES_ROOT = &H80000000
Public Const MAX_PATH = 256&
Public Const REG_SZ = 1
'************************************************************
' RUTINA QUE LE PERMITE ASOCIAR UN DETERMINADO
' TIPO DE FICHERO A UN PROGRAMA
' ASOCIA UN FICHERO CON EL BLOC DE NOTAS
' SE PUEDE CAMBIAR PARA ASOCIAR LOS QUE VD. QUIERA
'************************************************************
Public Const ERROR_SUCCESS = 0&
Public Const ERROR_BADDB = 1&
Public Const ERROR_BADKEY = 2&
Public Const ERROR_CANTOPEN = 3&
Public Const ERROR_CANTREAD = 4&
Public Const ERROR_CANTWRITE = 5&
Public Const ERROR_OUTOFMEMORY = 6&
Public Const ERROR_INVALID_PARAMETER = 7&
Public Const ERROR_ACCESS_DENIED = 8&
Global Const HKEY_CLASSES_ROOT = &H80000000
Public Const MAX_PATH = 256&
Public Const REG_SZ = 1
Private Sub Command1_Click()
Dim sKeyName As String ' NOMBRE DE LA CLAVE A REGISTRAR
Dim sKeyValue As String ' NOMBRE DEL VALOR A REGISTRAR
Dim ret& ' ERROR DEVUELTO POR LAS LLAMADAS A LA API
Dim lphKey& ' HANDLE A LA CREACION DE REGTKEY
sKeyName = "MyApp"
sKeyValue = "My Application"
ret& = RegCreateKey&(HKEY_CLASSES_ROOT, sKeyName, lphKey&)
ret& = RegSetValue&(lphKey&, "", REG_SZ, sKeyValue, 0&)
' CREA UNA ENTRADA EN LA RAIZ LLAMADA .BAR PARA ASOCIALARLA
CON "MyApp".
sKeyName = ".bar" '*

12. sKeyValue = "MyApp" '*
ret& = RegCreateKey&(HKEY_CLASSES_ROOT, sKeyName, lphKey&)
ret& = RegSetValue&(lphKey&, "", REG_SZ, sKeyValue, 0&)
' LINEA DE MANDATO "MyApp".
sKeyName = "MyApp" '*
sKeyValue = "notepad.exe %1" '*
ret& = RegCreateKey&(HKEY_CLASSES_ROOT, sKeyName, lphKey&)
ret& = RegSetValue&(lphKey&, "shellopencommand", REG_SZ, sKeyValue,
MAX_PATH)
End Sub
¿Como puedo saber el espacio libre que queda en el disco?
(FAT32)
'************************************************************
' LLAMADAS A LA API
'************************************************************
Declare Function GetDiskFreeSpaceEx Lib "kernel32" Alias _
"GetDiskFreeSpaceExA" (ByVal lpRootPathName As String, _
FreeBytesToCaller As LargeInt, BytesTotal As LargeInt, _
FreeBytesTotal As LargeInt) As Long
Type LargeInt
Bytes(0 To 7) As Byte
End Type
'************************************************************************
' DEVUELVE EL ESPACIO LIBRE DE UN DISCO FORMATEADO CON FAT32
'************************************************************************
Function GetFDS(Drive$)
Dim FreeBytesToCaller As LargeInt
BytesTotal As LargeInt
FreeBytesTotal
As LargeInt
Dim i%
GetDiskFreeSpaceEx Drive, FreeBytesToCaller, BytesTotal, FreeBytesTotal
For i = 0 to 7
GetFDS = GetFDS + FreeBytesToCaller.Bytes(i) * 2 ^ (8 * i)
Next i
End Function
¿Como copiar ficheros y que aparezcan los "papeles volando"?
Private Sub Form_Activate()
Dim result As Long
Dim fileop As SHFILEOPSTRUCT
Form1.Hide
With fileop
.hwnd = Me.hwnd
.wFunc = FO_COPY

13. .pFrom = "t:programsgestiongestion.exe" & vbNullChar & vbNullChar
.pTo = "c:calipso" & vbNullChar & vbNullChar
.fFlags = FOF_SIMPLEPROGRESS Or FOF_FILESONLY
End With
result = SHFileOperation(fileop)
If result <> 0 Then
MsgBox "Operación cancelada"
Else
If fileop.fAnyOperationsAborted <> 0 Then
MsgBox "Operación fallida"
End If
End If
Unload Form1
End Sub
' Para que no pregunte si se quiere sustituir el fichero destino, en caso de que
exista, añadir FOF_NOCONFIRMATION en la propiedad .fFlags =
FOF_SIMPLEPROGRESS Or
FOF_FILESONLY Or FOF_NOCONFIRMATION