FileAssociation

This article applies to Windows only.

See also: Multiplatform Programming Guide

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TFileAssociation

Author: Lainz

Licence: Modified LGPL

Version: 1.0

Description: This unit registers file association for Windows.

Download

GitHub: https://github.com/lainz/FileAssociation

Usage

First install the package. You can then drop the component TFileAssociation (FileAssoc unit) that gets installed in the System tab of the IDE on your form.

All parameters are mandatory. Especially ActionName which must be 'Open' to work with double click. This is useful as well for default commands like 'Edit' and 'Print'. This must be in English for 'Edit', 'Open' and 'Print' so it can access the right registry entry. You can customize the translation with ActionText.

...
uses
  ...
  FileAssoc; //<-- add fileassociation unit here

type

...
    { private declarations }
    assoc: TFileAssociation;
...

procedure TfrmMain.FormCreate(Sender: TObject);
begin
  assoc := TFileAssociation.Create(Self);//<-- create like a regular component
end;

procedure TfrmMain.Button1Click(Sender: TObject);
begin
  assoc.ApplicationName := 'Lazarus IDE';
  assoc.ApplicationDescription := 'RAD for Free Pascal';

  // you can change Extension and Action part for each extension you have

  assoc.Extension := '.lpr';
  assoc.ExtensionName := 'Lazarus Project';
  assoc.ExtensionIcon := '"C:\lazarus\images\lprfile.ico"';

  // full path required, you can use ParamStr(0) to get the path with the .exe name included. The path must be inside quotes if it has whitespace.
  assoc.Action := '"C:\lazarus\lazarus.exe" "%1"'; 
  assoc.ActionName := 'Open';
  assoc.ActionIcon := '"C:\lazarus\images\mainicon.ico"';

  // notice that using RegisterForAllUsers as True requires Administrator Privileges
  // if you want to run without privileges set it to false, but it will register for current user only
  assoc.RegisterForAllUsers:=False;
  if assoc.Execute then
  begin
    ShowMessage('OK');
    assoc.ClearIconCache; //<<-- rebuild icons
  end;
end;

end.

How to open the associated file

procedure TForm1.FormCreate(Sender: TObject);
var
  s: String;
begin
// if there are parameters
  if ParamCount > 0 then
  begin
// load the first parameter
    s := ParamStr(1);
 
// if is a .txt file
    if ExtractFileExt(s) = '.txt' then
    begin
// load the .txt file into a memo
      Memo1.Lines.LoadFromFile(s);
    end;
  end;
end;

Another way of registering file associations

Without using the component is as well possible to register a file association. This however doesn't cover adding the application to Default Programs, but is shorter if you only want to register a file type that's owned by your application.

{$IFDEF WINDOWS}
uses Registry, ShlObj;
 
procedure TMainForm.RegisterFileType(ExtName: string; AppName: string);
var
  reg: TRegistry;
begin
  reg := TRegistry.Create;
  try
    reg.RootKey := HKEY_CLASSES_ROOT;
    reg.OpenKey('.' + ExtName, True);
    reg.WriteString('', ExtName + 'file');
    reg.CloseKey;
    reg.CreateKey(ExtName + 'file');
    reg.OpenKey(ExtName + 'file\DefaultIcon', True);
    reg.WriteString('', AppName + ',0');
    reg.CloseKey;
    reg.OpenKey(ExtName + 'file\shell\open\command', True);
    reg.WriteString('', AppName + ' "%1"');
    reg.CloseKey;
  finally
    reg.Free;
  end;
  SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, nil, nil);
end;
{$ENDIF}

var
   reg: TRegistry;
       
begin
  {$IFDEF WINDOWS}
  reg := TRegistry.Create;
  try
    reg.RootKey := HKEY_CLASSES_ROOT;
    if not reg.KeyExists('ext' + 'file\shell\open\command') then
      RegisterFileType('ext', ExtractFilePath(Application.ExeName) + 'my_app.exe');
  finally
    reg.Free;
  end;
 
 if ParamCount > 0 then
  begin
    s := ParamStr(1);
    if ExtractFileExt(s) = '.ext' then
      LoadFile(s);
  end;
  {$ENDIF}

See also

If this component for some reason does not work for you, or you need to run it as administrator for all users without elevating your application privileges, an Inno Setup Script may fit your needs best.