Associating files programatically

Marco Gasi
Marco Gasi used Ask the Experts™
on
Hi all.

I have a small program which I use when I have to restore some file association silently modified by a new program installed. For instance I have recently installed VideoPad and it has associated many video files with itself without prompting for this. The code (working perfectly some time ago) is something like:

Extension := '.avi';
Prog := 'C:\Program files\VideoLAN\VLC\vlc.exe';

procedure writeAssociation(Extension, Prog: string);
var
  reg: TRegistry;
  Log: string;
begin
  Log := '';
  reg := TRegistry.Create;
  try
    try
      reg.RootKey := HKEY_CLASSES_ROOT;
      reg.LazyWrite := false;
      reg.OpenKey(Extension + '\shell\open\command', true);
      reg.WriteString('', Prog + ' %1');
      reg.CloseKey;
      reg.OpenKey(Extension + '\DefaultIcon', true);
      reg.WriteString('', Prog + ',0');
      reg.CloseKey;
      Log := 'File type ' + Extension + ' is now associated with ' + Prog;
    except
      Log := 'Association failed for file type ' + Extension;
    end;
  finally
    reg.free;
  end;
  mmo1.Lines.Add(Log);
end;

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Now this code changes the registry values correctly, but avi files are still opened by VideoPad when I double-click on them and the icon is not vlc icon but VideoPad one.

Now, my problem is not to reassociate the avi extension with vlc: I can do it manually. My problem is how to write a program which set the files associations in the registry and makes these associations be respected by Windows. That is, I have to understand why the registry values set by my code above are ignored by Windows.

Hope to have been clear.

Thanks in advance for any advice.

Cheers
Marco
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1) I wanted the option to "open with" from all file types so i added
  reg := TRegistry.Create;
  reg.RootKey := HKEY_CLASSES_ROOT;
  reg.LazyWrite := false;
  reg.OpenKey('*\OpenWithList\EncryptionSystem', true);
  reg.WriteString('','C:\Program Files\EncryptionSystem\EncryptionSystem.exe "%1"');
  reg.CloseKey;
  reg.free;

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If I look in the registry using regedit it's sure there as it should seem to be but when I right click on a file and select Open With it's not there...

So I then added this
 
 reg.OpenKey('*\shell\Encrypt\command', true);
  reg.WriteString('','C:\Program Files\EncryptionSystem\EncryptionSystem.exe "%1"');
  reg.CloseKey;

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Source: http://stackoverflow.com/questions/590892/windows-registry-file-association-menu
Marco GasiFreelancer
Top Expert 2010

Author

Commented:
Sorry, but i really don't see a solution in the source you posted.
Software architect
Top Expert 2012
Commented:
try my example:

uses ...  Registry, ShlObj;

procedure AssocFileExt(sExt, sFileName:String);
var
  reg: TRegistry;
  sExtWOPoint: String;
  buf: Byte;
begin
  sExt := Trim(sExt);
  if Length(sExt) = 0 then exit;
  sExtWOPoint := sExt;
  if sExtWOPoint[1] = '.' then Delete(sExtWOPoint, 1, 1);
  buf := 0;
  
  reg := TRegistry.Create;
  try
    reg.RootKey := HKEY_CLASSES_ROOT;
    if reg.OpenKey('\'+sExt, True) then
    begin
      reg.WriteString('', sExtWOPoint + 'file');
      reg.CloseKey;
      reg.OpenKey('\'+sExt+'\OpenWithList\ehshell.exe\', True);
      reg.CloseKey;
      if reg.OpenKey('\'+sExt+'\OpenWithProgIds\', True) then
      begin
        reg.WriteBinaryData(sExtWOPoint + 'file', buf, SizeOf(buf));
      end;
      reg.CloseKey;
      if reg.OpenKey('\'+sExtWOPoint + 'file\shell\open\command\', True) then
        reg.WriteString('', '"'+sFileName+'" "%1"');
      reg.CloseKey;
    end;

    reg.RootKey := HKEY_CURRENT_USER;
    if reg.OpenKey('\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\'+sExt+'\OpenWithProgids\', True) then
    begin
      reg.WriteBinaryData('avifile', buf, SizeOf(buf));
    end;
  finally
    reg.Free;
  end;
  SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, 0, 0);
end;

....
AssocFileExt('.avi', 'C:\Program files\VideoLAN\VLC\vlc.exe');

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... and here is another example

... for per user ext registration (and avoid admin rules) there is similar values under
HKEY_CURRENT_USER\SOFTWARE\Classes
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Marco GasiFreelancer
Top Expert 2010

Author

Commented:
Hi sinisav, ho do you do? :-)

Yes your code works: I didn't test it yet, but I know beacause I understood that I can simply empty the data of the default value to make the new association work.

Many thanks: you're becoming my personal expert ;-)

Merry Christmas and Happy New Year!
Marco GasiFreelancer
Top Expert 2010

Author

Commented:
Merry Christmas and Happy New Year!
Sinisa VukSoftware architect
Top Expert 2012

Commented:
Merry Christmas and successful New Year to you, your family and to all who comes to experts-exchange to expand their knowledge or share it as well.

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