Article ID: 258262 - Last Review: July 15, 2004 - Revision: 2.2

How To Write a DWORD to the Registry

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This article was previously published under Q258262

SUMMARY

Sometimes it is necessary to write information to the registry. This article shows how to write REG_DWORD values to a key created in the registry for this article. If the value you are writing does not already exist, you need to add it.

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MORE INFORMATION

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 (http://support.microsoft.com/kb/256986/EN-US/ ) Description of the Microsoft Windows Registry

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

The information about the registry editor in this article is for Microsoft Windows NT and Microsoft Windows 2000. If you are running Microsoft Windows 9X, you need to use Regedit.exe instead of Regedt32.exe.

NOTE: This article uses a registry key that is created just for testing purposes and should be deleted when you are done testing.

Start Registry Editor (Regedt32.exe).
Locate the following key in the registry:
```
   HKEY_LOCAL_MACHINE\Software
					
```
On the Edit menu, click Add Key, and then add the following registry Key:
```
   VfpREGTest
					
```

On the Edit menu, click Add Value, and then add the following registry value:

   Value Name: MyDWORD
   Data Type:  REG_DWORD
   Value:      0

Quit the Registry Editor.

From Visual FoxPro, create a program and enter the following code:

#DEFINE HKEY_CLASSES_ROOT           -2147483648
#DEFINE HKEY_CURRENT_USER           -2147483647
#DEFINE HKEY_LOCAL_MACHINE          -2147483646
#DEFINE HKEY_USERS                  -2147483645

LOCAL nKey, cSubKey, cValue, nValueToWrite, lSuccess
nKey = HKEY_LOCAL_MACHINE
nValueToWrite = 1
cSubKey = "Software\VfpREGTest"
cValue = "MyDWORD"

lSuccess = WriteRegDWORD(nKey, cSubKey, cValue, nValueToWrite)

IF (lSuccess) THEN
   =MESSAGEBOX("Function Successful.")
ELSE
   =MESSAGEBOX("Function Not Successful.")
ENDIF

FUNCTION WriteRegDWORD
   * This function writes a REG_DWORD to the registry. It will return .T.
   * if successful and .F. if it isn't successful.
   PARAMETERS  nKey, cSubKey, cValue,  nValueToWrite
   * nKey The root key to open. It can be any of the constants defined below.
   *#DEFINE HKEY_CLASSES_ROOT           -2147483648
   *#DEFINE HKEY_CURRENT_USER           -2147483647
   *#DEFINE HKEY_LOCAL_MACHINE          -2147483646
   *#DEFINE HKEY_USERS                  -2147483645
   *cSubKey The SubKey to open.
   *cValue The value that is going to be written.
   *nValueToWrite The value to write to the registry

   * Constants that are needed for Registry functions
   #DEFINE REG_DWORD   4

   * WIN 32 API functions that are used
   DECLARE Integer RegOpenKey IN Win32API ;
      Integer nHKey, String @cSubKey, Integer @nResult
   DECLARE Integer RegSetValueEx IN Win32API ;
      Integer hKey, String lpszValueName, Integer dwReserved,;
      Integer fdwType, String lpbData, Integer cbData
   DECLARE Integer RegCloseKey IN Win32API Integer nHKey

   * Local variables used
   LOCAL nErrCode          && Error Code returned from Registry functions
   LOCAL nKeyHandle        && Handle to Key that is opened in the Registry
   LOCAL lpdwValueType     && Type of Value that we are looking for.
   LOCAL lpbValue          && The data stored in the value
   LOCAL lpcbValueSize     && Size of the variable
   LOCAL lpdwReserved      && Reserved Must be 0

   * Initialize the variables
   nKeyHandle = 0
   lpdwReserved = 0           
   lpdwValueType = REG_DWORD
   lpcbValueSize = 4     && DWORD is 4 bytes

   lpbValue = LongToStr(nValueToWrite)

   nErrCode = RegOpenKey(nKey, cSubKey, @nKeyHandle)
   * If the error code isn't 0, then the key doesn't exist or can't be opened.
   IF (nErrCode # 0) THEN
      RETURN .F.
   ENDIF

   nErrCode=RegSetValueEx(nKeyHandle, cValue, lpdwReserved, lpdwValueType, lpbValue, lpcbValueSize)
   =RegCloseKey(nKeyHandle)
   IF (nErrCode # 0) THEN
      RETURN .F.
   ENDIF
RETURN .T.

FUNCTION LongToStr
* This function converts a long to a string
   PARAMETERS nLongVal
   LOCAL nLoopVar, strReturn

   strReturn = ""
   FOR nLoopVar = 24 TO 0 STEP -8
      strReturn = CHR(INT(nLongVal/(2^nLoopVar))) + strReturn
      nLongVal = MOD(nLongVal, (2^nLoopVar))
   NEXT
RETURN strReturn
* End of Code

Run the code created in step 1. A message box appears announcing the success or failure of the function. You can use regedt32.exe to verify that the value was written to the registry.
You can replace nKey, cSubKey, cValue, and nValueToWrite with your information to be written to the registry.