HOWTO: Associate File Extensions with a Custom Visual FoxPro Application

• Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a, 6.0
• Microsoft Windows versions 95, 98, 98 Second Edition
• Microsoft Windows NT 4.0

SUMMARY

Sometimes, developers may want to associate certain file extensions with a custom Visual FoxPro application. It may be desirable to perform certain actions on certain file types. For instance, the developer may want to run .ZZ0 files and edit .ZZ1 files. The following example demonstrates how to do this from Visual FoxPro using API calls.

MORE INFORMATION

NOTE: Developers will need Visual FoxPro 6.0 with Visual Studio 6.0 Service Pack 3 (VFP6_SP3) in order to RUN the custom files using the method outlined here. This is because the ability to compile programs through custom Visual FoxPro applications was introduced in VFP6_SP3.

Setting Up the Associations

1. Create a new text file on the Windows desktop with the following code inside. Save the file as RUNTEST.TXT:




MESSAGEBOX("HELLO!",48,"Associated Via API") 

2. Change the extension of this file from .TXT to .ZZ0. Click Yes when warned that the file may become unusable.



3. Make a copy of RUNTEST.ZZ0 on the Windows desktop and name the copy MODITEST.ZZ1.
   
   NOTE: The icon for these files should change to the Windows flag and double-clicking it should produce a dialog box titled "OPEN WITH." If this occurs, these file extensions are not associated with any application on the machine. If the dialog box titled OPEN WITH does not appear, there is an application installed that is associated with these extensions. DO NOT RUN THIS SAMPLE if this behavior occurs! Doing so may damage the file associations on the machine.



4. Open Visual FoxPro and copy the following code into a new program:




LOCAL nResult,nDisplay, cKeyName, cKeyValue, nKeyLen
#DEFINE SECURITY_ACCESS_MASK 983103     && SAM value KEY_ALL_ACCESS
#DEFINE SHCNE_ASSOCCHANGED   0x08000000
#DEFINE HKEY_CLASSES_ROOT    -2147483648
#DEFINE SHCNF_IDLIST         0x0000

DECLARE RegCreateKeyEx IN ADVAPI32.DLL;
	INTEGER,STRING,INTEGER,STRING,INTEGER,INTEGER,INTEGER,INTEGER @, INTEGER @

DECLARE RegSetValueEx IN ADVAPI32.DLL;
	INTEGER,STRING,INTEGER,INTEGER,STRING,INTEGER

DECLARE RegCloseKey IN ADVAPI32.DLL	INTEGER nHKey

DECLARE SHChangeNotify IN Shell32.DLL INTEGER, INTEGER, STRING, STRING

*~ This creates a Root entry called "aaApp."
nResult=0
nDisplay=0
cKeyName = "aaAPP"
cKeyValue = "My Application"
nKeyLen = LEN(cKeyValue)
RegCreateKeyEx(HKEY_CLASSES_ROOT,cKeyName ,0,"REG_SZ", ;
	0,SECURITY_ACCESS_MASK,0,@nResult,@nDisplay)
RegSetValueEx(nResult,"",0,1,cKeyValue ,nKeyLen)
RegCloseKey(@nResult)

*~ This creates a Root entry called .ZZ0 associated with "aaApp." 
nResult= 0
nDisplay = 0
cKeyName = ".ZZ0"
cKeyValue = "aaApp"
nKeyLen = LEN(cKeyValue)
RegCreateKeyEx(HKEY_CLASSES_ROOT,cKeyName,0,"REG_SZ",;
	0,SECURITY_ACCESS_MASK,0,@nResult,@nDisplay)
RegSetValueEx(nResult,"",0,1,cKeyValue,nKeyLen)
RegCloseKey(@nResult)

*~ This creates a Root entry called .ZZ1 associated with "aaApp." 
nResult= 0
nDisplay = 0
cKeyName = ".ZZ1"
cKeyValue = "aaApp"
nKeyLen = LEN(cKeyValue)
RegCreateKeyEx(HKEY_CLASSES_ROOT,cKeyName,0,"REG_SZ",;
	0,SECURITY_ACCESS_MASK,0,@nResult,@nDisplay)
RegSetValueEx(nResult,"",0,1,cKeyValue,nKeyLen)
RegCloseKey(@nResult)

*~ This sets the command line for files associated with "aaApp." 
*~ The path will need to be adjusted.
nResult= 0
nDisplay = 0
cKeyName = "aaApp\shell\open\command"
*~ ADJUST THIS PATH TO REFLECT YOUR DIRECTORY STRUCTURE.
*~
cKeyValue = "C:\WINDOWS\Desktop\testexe.exe %1"
*~
*~
nKeyLen = LEN(cKeyValue)
RegCreateKeyEx(HKEY_CLASSES_ROOT,cKeyName,0,"REG_SZ",;
	0,SECURITY_ACCESS_MASK,0,@nResult,@nDisplay)
RegSetValueEx(nResult,"",0,1,cKeyValue,nKeyLen)
RegCloseKey(@nResult)

*~ Code to refresh icons after association.
SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL)<BR/>
CLEAR DLLS 

5. Adjust the following line so the path reflects the DESKTOP directory on the current machine (TESTEXE.EXE will be built later):




cKeyValue = "C:\WINDOWS\Desktop\testexe.exe %1" 

6. Save the program as "KB_ASSOC.PRG."

Building the Test Executable

1. Open a new project in Visual FoxPro.



2. Create a new program through the Code tab with the following code. Save the program as Main.prg:




*~ Double-clicking the file passes its full path to the
*~ associated program (this .EXE).
LPARAMETER cFileName
#DEFINE MB_OK                   0       && OK button only
#DEFINE MB_ICONINFORMATION      64      && Information icon
SET SYSMENU OFF
_SCREEN.CAPTION = "Test Executable"

*~ Check extension of passed file name.
DO CASE
	CASE UPPER(RIGHT(cFileName,3)) = "ZZ0"
*~ This code checks for VFP 6 SP3.
*~ Exits if anything but.
   IF !("06.00.8492.00" $ ALLT(VERS()))
      MESSAGEBOX("Not using VFP6 SP3. Needed to 'COMPILE' in an .EXE.", ;
         MB_ICONINFORMATION + MB_OK,"Exiting")
      RETURN
   ENDIF
* File extension is .ZZO and you are in VFP6 SP3. Compile and run.
   COMPILE (cFileName)
   DO (cFileName)
   CASE UPPER(RIGHT(cFileName,3)) = "ZZ1"
*~ File is .ZZ1, so modify it. Not VFP6SP3 dependant.
      MODI COMM (cFileName)
   ENDCASE 

3. Associate a custom icon with the project and build the project into an executable named TESTEXE.EXE. Save it to the Windows Desktop.

Running the Test

1. Inside Visual FoxPro, run the "KB_ASSOC.PRG" program created earlier. Notice that the MODITEST.ZZ0 and RUNTEST.ZZ1 files on the Windows desktop have changed appearance: they now display the icon of the TESTEXE.EXE or a Visual FoxPro icon.



2. Go to the Windows desktop and double-click the RUNTEST.ZZ0. The TEXTESE.EXE will start and the "HELLO" message box will appear.



3. Now, double-click the MODITEST.ZZ1 file. The TESTEXE.EXE will start and the file will be opened for modification. Close the edit window to exit.

Cleaning Up

1. Back inside Visual FoxPro, copy the following code into a new program file. Save the program as CLEANUP.PRG:




*!* After the demo has run, use this program to remove the registry keys it created.
#DEFINE SHCNE_ASSOCCHANGED   0x08000000
#DEFINE HKEY_CLASSES_ROOT    -2147483648
#DEFINE SHCNF_IDLIST         0x0000
FILE_KEY1 = ".ZZ0"
FILE_KEY2 = ".ZZ1"
EXE_KEY0 = "aaAPP\shell\open\command"
EXE_KEY1 = "aaAPP\shell\open"
EXE_KEY2 = "aaAPP\shell"
EXE_KEY3 = "aaAPP"

DECLARE RegDeleteKey IN ADVAPI32.DLL INTEGER, STRING
DECLARE SHChangeNotify IN Shell32.DLL INTEGER, INTEGER, STRING, STRING

RegDeleteKey(HKEY_CLASSES_ROOT,FILE_KEY1)
RegDeleteKey(HKEY_CLASSES_ROOT,FILE_KEY2)
RegDeleteKey(HKEY_CLASSES_ROOT,EXE_KEY0)
RegDeleteKey(HKEY_CLASSES_ROOT,EXE_KEY1)
RegDeleteKey(HKEY_CLASSES_ROOT,EXE_KEY2)
RegDeleteKey(HKEY_CLASSES_ROOT,EXE_KEY3)
SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL)

CLEAR DLLS 

2. Run CLEANUP.PRG to delete the registry entries created earlier. The icons of the two desktop files should revert back to the Windows flag.

Additional query words:

Keywords          : kbAPI kbNTOS kbVFp300 kbVFp300b kbVFp500 kbVFp500a kbVFp600 kbWinOS95 kbWinOS98 kbGrpFox kbDSupport 
Version           : WINDOWS:5.0,5.0a,6.0,95,98,98 Second Edition; winnt:4.0
Platform          : WINDOWS winnt 
Issue type        : kbhowto 

Last Reviewed: August 12, 1999