// If an application asks user to select an icon, it's
// more convenient for the user to see list of files as
// large icons instead of small icons. Also, for selecting
// an image file, user will be happier to choose an image
// by seeing the thumbnails.
// The standard file dialog initialy shows the files in
// the LIST (small icon) style, and there is no documented
// way to change this behavior. So, if user wants to see
// the file list in another style, she/he should change
// it manually by selecting the desired view style form
// the provided popup menu.
// Here is a workaround for this limitation to select the
// reasonable view style for a file dialog.
type
 TFileViewStyle = (fvsIcons, fvsList, fvsDetails, fvsThumbnails, fvsTiles);
function SetFileDialogViewStyle(Handle: THandle; ViewStyle: TFileViewStyle): Boolean;
const
 CommandIDs: array[TFileViewStyle] of Word = ($7029, $702B, $702C, $702D, $702E);
var
 NotifyWnd: THandle;
begin
 Result := False;
 NotifyWnd := FindWindowEx(GetParent(Handle), 0, 'SHELLDLL_DefView', nil);
 if NotifyWnd <> 0 then
 begin
  SendMessage(NotifyWnd, WM_COMMAND, CommandIDs[ViewStyle], 0);
  Result := True;
 end;
end;
// Each time the file dialog opens, the above function should
// be called to set the desired view style. The OnShow event
// of the file dialogs seems to be the right place for this
// purpose, however at that time the list is not created yet
// and the function fails.
// When the file list is created, the dialog raises two events:
// OnFolderChange and OnSelectionChange events. We can use one
// of these events for our purpose. However, we have to consider
// that the function should be called just once for each show.
// Here is a sample usage of the introduced function:
procedure TForm1.Button1Click(Sender: TObject);
begin
 OpenDialog1.Tag := 0;
 OpenDialog1.Execute;
end;
procedure TForm1.OpenDialog1FolderChange(Sender: TObject);
begin
 if OpenDialog1.Tag = 0 then
 begin
  SetFileDialogViewStyle(OpenDialog1.Handle, fvsIcons)
  OpenDialog1.Tag := 1;
 end;
end;