McGrath Electronics, Inc. Provides Network Support in Phoenix, AZ

Function to Read Values from the Windows Registry (Delphi)

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The Delphi TRegistry function CreateKey fails when the user is not logged in with administrative rights. The cause of this problem is that by default Delphi opens the Windows registry with security access of KEY_ALL_ACCESS. Even the Delphi function OpenKeyReadOnly opens the registry with the security access value KEY_ALL_ACCESS.

This is a major problem since you should store shared information about your program in HKEY_LOCAL_MACHINE (HKLM) so all users of the computer have access to the settings. However, especially on a network users should never be setup as administrators. To get around this problem when your program needs to access values in the registry, you can use the standard Windows API functions RegOpenKeyEx, RegQueryValueEx, and RegCloseKey. The RegOpenKeyEx allows you to set the security access to a lower level such as KEY_READ. KEY_READ should be the only access required by standard users.

I use the Delphi TRegistry methods to create registry keys when the program is first run and then use the Windows API functions when I need to read registry keys. This system works well for me when I deploy my software on networks. My software must first be run by a user with administrative rights so various paths to the network control and data directories can be set. After the initial run any user of the computer can read the necessary paths.

Below is the unit I use to read registry keys with the software I develop. You can also click here to download the unit I use to read the registry information. Feel free to add this unit to your software. If you have any comments or questions please feel free to email me.

unit ReadRegistryInfo;
{This unit reads a value from the the registry
 HKEY_LOCAL_MACHINE. It accepts the SubKey you want to open and
 the name of the value you want to know as input paramters. It 
 returns the values data or ERROR if there was a problem.}

interface

uses WinTypes;

function ReadRegEntry(strSubKey,strValueName: string): string;
 var
  Key: HKey;
  Buffer: array[0..255] of char;
  Size: cardinal;
 begin
  Result := 'ERROR';
  Size := SizeOf(Buffer);
  If RegOpenKeyEx(HKEY_LOCAL_MACHINE,
   PChar(strSubKey),0,KEY_READ,Key) = ERROR_SUCCESS Then
    if RegQueryValueEx(Key,PChar(strValueName),nil,nil,
     @Buffer,@Size) = ERROR_SUCCESS then
      Result := Buffer;
  RegCloseKey(Key);
 end;

end.

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