if OpenDialog1.Execute then
  Memo1.Lines.LoadFromFile(OpenDialog1.FileName)
else
  Memo1.Lines.Clear;

if (OpenDialog1->Execute())
  Memo1->Lines->LoadFromFile(OpenDialog1->FileName);
else
  Memo1->Clear();

/*
The following code allows the user to use a dialog box to
redefine the icon for the application at run time. When the
user clicks Button1, OpenDialog1 executes and the user
specifies an icon filename. The Icon is then assigned to the
application.  At runtime, click Button1 to select the icon,
then minimize the application to see the icon.
*/
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  OpenPictureDialog1->DefaultExt = GraphicExtension(__classid(TIcon));
  OpenPictureDialog1->FileName = GraphicFileMask(__classid(TIcon));
  OpenPictureDialog1->Filter = GraphicFilter(__classid(TIcon));
  OpenPictureDialog1->Options.Clear();
  OpenPictureDialog1->Options << ofFileMustExist << ofHideReadOnly << ofNoChangeDir;
  while (true)
  {
    if (OpenPictureDialog1->Execute())
    {
      if (!OpenPictureDialog1->Options.Contains(ofExtensionDifferent))
      {
        Application->Icon->LoadFromFile(OpenPictureDialog1->FileName);
        break;
      }
      else // reset Options to remove ofExtensionDifferent
      {
        OpenPictureDialog1->Options.Clear();
        OpenPictureDialog1->Options << ofFileMustExist << ofHideReadOnly << ofNoChangeDir;
      }
    }
    else // user cancelled
      break;
  }
}

{
The following code allows the user to use a dialog box to
redefine the icon for the application at run time. When the
user clicks Button1, OpenDialog1 executes and the user
specifies an icon filename. The Icon is then assigned to the
application.  At runtime, click Button1 to select the icon,
then minimize the application to see the icon.
}
procedure TForm1.Button1Click(Sender: TObject);
var 
Done: Boolean;
filenamestring : String;
begin
  OpenPictureDialog1.DefaultExt := GraphicExtension(TIcon);
  filenamestring := GraphicFileMask(TIcon);
  OpenPictureDialog1.FileName := filenamestring;
  OpenPictureDialog1.Filter := GraphicFilter(TIcon);
  OpenPictureDialog1.Options := [ ofFileMustExist, ofHideReadOnly, ofNoChangeDir ];
  Done := False;
  while not Done do
  begin
  if OpenPictureDialog1.Execute then
    begin
    if not (ofExtensionDifferent in OpenPictureDialog1.Options) then
      begin
      Application.Icon.LoadFromFile(OpenPictureDialog1.FileName);
      Done := True;
      end
    else
//      OpenPictureDialog1.Options := OpenPictureDialog1.Options - ofExtensionDifferent;
    end
  else { User cancelled }
    Done := True;
  end;
end; 

{
Use a TOpenDialog to select a file.  Place the first line of
the file into a TEdit.  Click on the text edit to open the
open dialog box. 
}
procedure TForm1.Edit1Click(Sender: TObject);
var
  F: TextFile;
  S: string;
begin
  if OpenDialog1.Execute then            { Display Open dialog box }
  begin
    AssignFile(F, OpenDialog1.FileName); { File selected in dialog }
    Reset(F);
    Readln(F, S);                        { Read first line of file }
    Edit1.Text := S;                     { Put string in a TEdit control }
    CloseFile(F);
  end;
end;

{
This example uses a memo box, two buttons, an open dialog
and a save dialog on a form. When the application runs,
the open dialog and save dialog filters are initialized,
so to open and save *.txt files or files with any extension.
Clicking on the Open/Save button executes the open/save dialog.
An exception is raised when trying to open a file that
does not exist, or when trying to overwrite a file using the
save dialog.
}
procedure TForm1.Button1Click(Sender: TObject);
begin
  { execute an open file dialog }
  if OpenDialog1.Execute then
    { first check if file exists }
    if FileExists(OpenDialog1.FileName) then
      { if it exists, load the data into the memo box }
      Memo1.Lines.LoadFromFile(OpenDialog1.FileName)
    else
      { otherwise raise an exception }
      raise Exception.Create('File does not exist.');
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  { execute a save file dialog }
  if SaveDialog1.Execute then
    { first check if file exists }
    if FileExists(SaveDialog1.FileName) then
      { if it exists, raise an exception }
      raise Exception.Create('File already exists. Cannot overwrite.')
    else
      { otherwise, save the memo box lines into the file }
      Memo1.Lines.SaveToFile(SaveDialog1.FileName);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  {
  initialize the dialog filters to open/save *.txt files
  and also files with arbitrary extension
  }
  OpenDialog1.Filter := 'Text files (*.txt)|*.TXT|Any file (*.*)|*.*';
  SaveDialog1.Filter := 'Text files (*.txt)|*.TXT|Any file (*.*)|*.*';
end;