Не могу поправить программку - PascalABC.NET

unit Unit1;
 
interface
 
uses
  System, System.Drawing, System.Windows.Forms;
 
type
  Form1 = class(Form)
    procedure button1_Click(sender: Object; e: EventArgs);
    procedure button2_Click(sender: Object; e: EventArgs);
    procedure button3_Click(sender: Object; e: EventArgs);
  {$region FormDesigner}
  private
    {$resource Unit1.Form1.resources}
    button2: Button;
    button3: Button;
    button1: Button;
    {$include Unit1.Form1.inc}
  {$endregion FormDesigner}
  public 
    constructor;
    begin
      InitializeComponent;
    end;
  end;
 
implementation
 
var
  gpath: string;
  gpath2: string;
  
procedure Form1.button1_Click(sender: Object; e: EventArgs);// Файл f
var
  open: System.Windows.Forms.OpenFileDialog;
  error: boolean;
begin
  gpath := '';
  try
    open := new OpenFileDialog();
    if open.ShowDialog() = System.Windows.Forms.DialogResult.OK then 
      gpath := open.FileName;
  except
    MessageBox.Show('Не удалось открыть файл');
    error := true;
  end;
  if error then exit;
end;
 
procedure Form1.button2_Click(sender: Object; e: EventArgs);// Файл g
var
  f, g: file of char;
  i, j: integer;
  x: char; 
  str: string;
  error: boolean;
begin
  str := 'qwertyuioplkjhgfdsazxcvbnm';
  j := 0;
  if (gpath = '') or (gpath2 = '') then messagebox.Show('Не был выбран один из файлов', 'Ошибка') else
  begin
    error := false;
    try
      Assign(f, gpath); 
      Reset(f);
    except
      MessageBox.Show('Error');
      error := true;
    end;
    if error then exit;
    
    try
      Assign(g, gpath2);
      rewrite(g);
    except
      MessageBox.Show('Error');
      error := true;
      CloseFile(f);    
    end;
    try
      for i := 1 to FileSize(f) do     
      begin
        read(f, x);
        if str.Contains(x) then
        begin
          write(g, x);
        end;
      end;
    finally
      CloseFile(f);
      CloseFile(g);
    end;
  end;
end;
 
procedure Form1.button3_Click(sender: Object; e: EventArgs);//Запись
var
  open: System.Windows.Forms.OpenFileDialog;
begin
  gpath2 := '';
  try
    open := new OpenFileDialog();
    if open.ShowDialog() = System.Windows.Forms.DialogResult.OK then 
      gpath2 := open.FileName;
  except
    on System.IO.IOException do MessageBox.Show('Error');
  end;
end;
 
end.