RegSetValueEx

This function stores data in the value field of an open registry key. It can also set additional value and type information for the specified key.

LONG RegSetValueEx( 
HKEY hKey, 
LPCWSTR lpValueName, 
DWORD Reserved, 
DWORD dwType, 
const BYTE *lpData, 
DWORD cbData ); 

Parameters

• hKey
  [in] Handle to a currently open key or any of the following predefined reserved handle values:

  • HKEY_CLASSES_ROOT
  • HKEY_CURRENT_USER
  • HKEY_LOCAL_MACHINE
  • HKEY_USERS

• lpValueName
  [in] Pointer to a string containing the name of the value to set. If a value with this name is not already present in the key, the function adds it to the key. If this parameter is NULL or an empty string, the function sets the type and data for the keys unnamed value. Registry keys do not have default values, but they can have one unnamed value, which can be of any type. The maximum length of a value name is 255, not including the terminating NULL character.

• Reserved
  [in] Reserved; must be zero.

• dwType
  [in] Specifies the type of information to be stored as the values data. This parameter can be one of the following values:

  Value	Description
  REG_BINARY	Binary data in any form.
  REG_DWORD	A 32-bit number.
  REG_DWORD_LITTLE_ENDIAN	A 32-bit number in little-endian format. This is equivalent to REG_DWORD.
  	In little-endian format, a multi-byte value is stored in memory from the lowest byte (the little end) to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.
  REG_DWORD_BIG_ENDIAN	A 32-bit number in big-endian format.
  	In big-endian format, a multi-byte value is stored in memory from the highest byte (the big end) to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.
  REG_EXPAND_SZ	A null-terminated string that contains unexpanded references to environment variables (for example, %PATH%).
  REG_LINK	A Unicode symbolic link. Used internally; applications should not use this type.
  REG_MULTI_SZ	An array of null-terminated strings, terminated by two null characters.
  REG_NONE	No defined value type.
  REG_RESOURCE_LIST	A device-driver resource list.
  REG_SZ	A null-terminated string.
  	Do not use the REG_SZ type to store hard-coded paths to the system root directory or to the drive containing the system files. Instead, use the REG_EXPAND_SZ type with environment variables such as "%SystemRoot%". This ensures that the path will be up-to-date even if the user remaps the system drive to a different drive letter.

• lpData
  [in] Pointer to a buffer containing the data to be stored with the specified value name.

• cbData
  [in] Specifies the size, in bytes, of the information pointed to by the lpData parameter. If the data is of type REG_SZ, REG_EXPAND_SZ, or REG_MULTI_SZ, cbData must include the size of the terminating null character. The maximum size of data allowed in Windows CE is 4 KB.

Return Values

ERROR_SUCCESS indicates success. A nonzero error code defined in Winerror.h indicates failure. To get a generic description of the error, call FormatMessage with the FORMAT_MESSAGE_FROM_SYSTEM flag set. The message resource is optional; therefore, if you call FormatMessage it could fail.

Remarks

Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the registry. This helps the registry perform efficiently. Application elements such as icons, bitmaps, and executable files should be stored as files and not be placed in the registry.

Windows CE supports only the Unicode version of this function.

Requirements

Note   This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

RegCreateKeyEx, RegOpenKeyEx, RegQueryValueEx

 Last updated on Tuesday, July 13, 2004

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