Elevating Tasks in Vista

One of the Stonefield Query dialogs has a command button that allows the user to launch the ODBC Administrator, likely because they need to set up or modify a DSN. The button has "ODBC Admin" as its Caption and the following code in Click:

lcSystem = Thisform.oUtility.GetSystemDirectory()
try
  run /n1 &lcSystem..odbcad32.exe
catch
endtry

(GetSystemDirectory is a utility method that returns the location of the Windows System folder; I'll show the code for that later.)

This worked great until I tried it on Vista; it fails there because the ODBC Administrator requires admin privileges and the RUN command doesn't support requesting elevation. Fortunately, there's an easy solution to that: use ShellExecute instead. I changed the code to:

lcSystem = oUtility.GetSystemDirectory()
try
  oUtility.ShellExecute(lcSystem + 'odbcad32.exe', 'RunAs')
catch
endtry

(Like GetSystemDirectory, ShellExecute is another utility function. It runs the specified command. The cool thing about ShellExecute is that it'll launch the appropriate program. In the case of an EXE, it runs it. In the case of an HTML file, it launches the default browser. In the case of a DOC file, it launches Word.)

Now when the user clicks the button, they're requested to elevate to administrator before the ODBC Administrator appears. To make it obvious that this will happen, I've followed the Vista convention of adding a shield image to the button to alert the user that elevation will be requested. To do that, I set PicturePosition to 1-Left of Caption, Picture to VistaShield.BMP (an image I created using SnagIt to grab the shield icon displayed in the User Accounts control panel applet), and shortened Caption to just "ODBC" so it all fits. Here's what the button looks like:



Here's the code for GetSystemDirectory:

#define cnMAX_PATH 260
#define ccNULL chr(0)
local lcBuffer
lcBuffer = space(cnMAX_PATH)
declare integer GetSystemDirectory in Win32API ;
  string @szBuffer, integer nLength
GetSystemDirectory(@lcBuffer, cnMAX_PATH)
return addbs(alltrim(left(lcBuffer, at(ccNULL, lcBuffer) - 1)))

Here's the code for ShellExecute:

lparameters tcFileName, ;
  tcOperation, ;
  tcWorkDir, ;
  tcParameters
local lcFileName, ;
  lcWorkDir, ;
  lcOperation, ;
  lcParameters, ;
  lnShow
if empty(tcFileName)
  return -1
endif empty(tcFileName)
lcFileName   = alltrim(tcFileName)
lcWorkDir    = iif(vartype(tcWorkDir) = 'C', alltrim(tcWorkDir), '')
lcOperation  = iif(vartype(tcOperation) = 'C' and not empty(tcOperation), ;
  alltrim(tcOperation), 'Open')
lcParameters = iif(vartype(tcParameters) = 'C', alltrim(tcParameters), '')
lnShow       = iif(upper(lcOperation) = 'Print', 0, 1)
declare integer ShellExecute in SHELL32.DLL ;
  integer nWinHandle, ; && handle of parent window
  string cOperation, ; && operation to perform
  string cFileName, ;  && filename
  string cParameters, ; && parameters for the executable
  string cDirectory, ; && default directory
  integer nShowWindow  && window state
return ShellExecute(0, lcOperation, lcFilename, lcParameters, lcWorkDir, ;
  lnShow)