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Another registry class

, 25 Apr 2003 CPOL
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A registry class with overloaded operators to use registry values like normal variables


In many projects I need to store simple strings, DWORDS or for window position CRect's in the registry. I know there are many registry classes out there, so why one more?

The answer: simplicity. I want to write to the registry as easy as assigning a value to a variable. Like an eeprom variable in neuron controllers (those of you who use those controllers know what I mean). So I wrote exactly such a class.


So, how to use this class - or better classes. I wrote a separate class for CString, DWORD, CRect and CPoint.

// initialize the variables
CRegString mystring("Software\\Company\\Subkey\\MyString", "defaultvalue");
CRegRect   myrect("Software\\Company\\Subkey\\MyRect", CRect(1,1,1,1));
CRegDWORD  myword("Software\\Company\\Subkey\\mydword", 100, 
                     TRUE, HKEY_LOCAL_MACHINE);
CRegPoint  mypoint("Software\\Company\\Subkey\\mypoint");

// now use those variables
CString str = mystring;     //if registry does not exist, the default value is used
mystring = "TestValue";     //"TestValue" is stored in the registry
mystring += "!";            //now the registry value MyString contains "TestValue!"
myrect = CRect(100,200,300,400);    //store in the registry
LPRECT lpR = (LPRECT)myrect;
myword = GetTickCounts();   //just an example
mypoint = CPoint(0,0);

As you can see, once the CRegXXX object knows to which registry key/value it is assigned to you can use it like any other variable!

To avoid too much access to the registry the value is cached. Writes occur only if the new value is different than the current value. Reads occur only once in the constructor. Since such a cached behaviour could lead to some problems, you can force reads and writes to the registry with the methods read() and write(). To disable the cache and force the class to always access the registry just set that in the constructor. the constructor for the CRegDWORD looks like this:

* Constructor.
* @param key the path to the key, including the key. 
*            example: "Software\\Company\\SubKey\\MyValue"
* @param def the default value used when the key does not exist or 
*            a read error occured
* @param force set to TRUE if no cache should be used, i.e. always read and write 
*              directly from/to registry
* @param base a predefined base key like HKEY_LOCAL_MACHINE. see the SDK 
*             documentation for more information.
CRegDWORD(CString key, DWORD def = 0, BOOL force = FALSE, 
          HKEY base = HKEY_CURRENT_USER);

The classes CRegString, CRegRect and CRegPoint have similar constructors. See the header files for details.

Not all methods of the "base" classes are overloaded. So if you want to, for example, use some methods of the CString class you have to typecast the CRegString to a CString first:

int l = ((CString)mystring).GetLength();

Please note that in the second line where the Trim() is used that the changed string is NOT written to the registry!

And please: keep your complaints about "not again a registry class" and the like for yourselves. If you don't like it, don't use it!


  • 2. April 2003 :
    1. added classes for use without MFC: CRegStdString, CRegStdDWORD
    2. now compiles for UNICODE too
  • 9. July 2002 :
    1. Corrected a bug found by Hans Dietrich
    2. Extended the classes with two methods: removeKey() and removeValue()

Daniel Andersson wrote a templatized version of this class. See his article here.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer
Switzerland Switzerland

Comments and Discussions

GeneralMy vote of 5 Pinmemberdespana5-Feb-13 12:29 
QuestionBug for Unicode projects? Pinmemberrh_20-Apr-07 3:26 
GeneralModified to read REG_MULTI_SZ correctly PinmemberDouglas R. Keesler23-Dec-06 5:54 
Generaltab ctrl Pinmemberlocoone2-Sep-06 14:29 
GeneralNice... PinmemberHumanJHawkins14-Jun-06 12:39 
Generalunicode for registry Pinmemberraycadarena13-Feb-06 19:45 
GeneralNeed error handling PinmemberCharlieG28-Jul-05 7:08 
GeneralVery nice, thank you a lot! PinmemberAlex Chirokov4-Jul-05 17:47 
GeneralConstructor / read problem PinmemberBob Stanneveld13-Apr-05 4:08 
Generalerror C2039: 'Trim' : is not a member of 'CString' Pinmemberqiek4-Nov-04 6:07 
GeneralRe: error C2039: 'Trim' : is not a member of 'CString' PinmemberEvanTao30-Nov-04 1:03 
GeneralRe: error C2039: 'Trim' : is not a member of 'CString' PinmemberAlex Chirokov4-Jul-05 17:52 
AnswerRe: error C2039: 'Trim' : is not a member of 'CString' PinmemberDouglas R. Keesler23-Dec-06 6:30 
Generalexport registry as text file programmatically Pinmemberyamei14-Oct-04 13:28 
GeneralLinker error wtih removeKey() PinmemberJR Cooper7-Oct-04 14:34 
GeneralRe: Linker error wtih removeKey() Pinmembermnowok12-Oct-04 1:07 
Generali can write to the registry, yaay! Pinmemberasmotritsky20-Jun-04 0:33 
GeneralUse in DLL that does not use MFC Pinmemberltang724-Apr-04 20:01 
General"Simple" is great! PinmemberXeonSniper13-Apr-04 18:40 
Generalloading .reg file programmatically Pinmemberbruno leclerc18-Mar-04 2:14 
GeneralCRegStdDWORD instead of CRegStdWORD Pinmemberujohnc0016-Mar-04 11:11 
GeneralGreat! thank you PinmemberPMartos18-Dec-03 10:14 
GeneralFelicidades :) PinmemberC++17-Dec-03 9:41 
QuestionBug? PinmemberIgor Vigdorchik16-Dec-03 10:29 
AnswerRe: Bug? PinmemberJonas Nordlund6-Feb-04 0:50 
GeneralRe: Bug? PinmemberIgor Vigdorchik6-Feb-04 19:03 
GeneralDid not compile with VC6 PinmemberJacques Cooper12-Dec-03 14:16 
GeneralRe: Did not compile with VC6 PinmemberJonas Nordlund6-Feb-04 0:55 
Generalcool code... a lot of thanks and a suggestion... PinmemberpHreak081528-Sep-03 5:11 
GeneralGreat PinmemberBEamer18-Sep-03 20:32 
GeneralHere's how to read/write to REG_MULTI_SZ Pinmemberunivega_r30410-Aug-03 19:13 
GeneralRe: Here's how to read/write to REG_MULTI_SZ Pinsussjfernb3-Jun-04 12:07 
GeneralRe: Here's how to read/write to REG_MULTI_SZ Pinmemberunivega_r30422-Dec-04 8:15 
GeneralRe: Here's how to read/write to REG_MULTI_SZ PinmemberMoSs.gr3-Nov-04 8:56 
GeneralRe: Here's how to read/write to REG_MULTI_SZ Pinmemberfarzadb8-Apr-05 13:31 
QuestionHow to use as a member variable? PinmemberSorak26-May-03 20:40 
AnswerRe: How to use as a member variable? PinmemberSteveKing27-May-03 0:04 
AnswerRe: How to use as a member variable? PinmemberChris Richardson27-May-03 17:47 
GeneralBeautiful Pinmember=[ Abin ]=1-Apr-03 3:51 
Generala little problem working with UNICODE Pinmembernothingremained10-Nov-02 21:16 
GeneralRe: a little problem working with UNICODE PinmemberTDWiseley8-Jan-03 15:11 
GeneralTrim PinmemberDins_C10-Sep-02 11:20 
GeneralRe: Trim PinmemberSteveKing11-Sep-02 4:00 
GeneralCould you help me please! PinsussAnonymous14-Jul-02 19:14 
GeneralRe: Could you help me please! PinmemberSteveKing15-Jul-02 7:05 
GeneralRe: Could you help me please! Pinmemberunivega_r3049-Aug-03 6:25 
GeneralQuestion about new removeKey function PinmemberHans Dietrich10-Jul-02 10:36 
GeneralRe: Question about new removeKey function PinmemberSteveKing10-Jul-02 22:35 
GeneralVery nice! but one bug... PinmemberHans Dietrich8-Jul-02 9:40 
In several place in your code you have:

          char *pStr = " ";
          RegQueryValueEx(m_hKey, m_key, NULL, &type, (BYTE*) pStr, (LPDWORD) &size);
          pStr = new char[size];
          if (RegQueryValueEx(m_hKey, m_key, NULL, &type, (BYTE*) pStr,(LPDWORD) &size)==ERROR_SUCCESS)
               m_value = CString(pStr);
               delete pStr;

This should be changed to:

          RegQueryValueEx(m_hKey, m_key, NULL, &type, NULL, (LPDWORD) &size);
          char *pStr = new char[size];
          if (RegQueryValueEx(m_hKey, m_key, NULL, &type, (BYTE*) pStr,(LPDWORD) &size)==ERROR_SUCCESS)
               m_value = CString(pStr);
               delete [] pStr;
(note [] after delete).

Best wishes,

GeneralRe: Very nice! but one bug... PinmemberSteveKing9-Jul-02 0:01 

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