Form1_2

unit LabForm1_2;

interface

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.Menus;

type
  TMainForm = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    InputNumber: TEdit;
    CalculateButton: TButton;
    OutputLabel: TLabel;
    OpenDialog: TOpenDialog;
    SaveDialog: TSaveDialog;
    MainMenu: TMainMenu;
    FileMenu: TMenuItem;
    OpenFile: TMenuItem;
    SaveInFile: TMenuItem;
    Procedure Calculate(Num: Integer);
    procedure CalculateButtonClick(Sender: TObject);
    procedure OpenFileClick(Sender: TObject);
    procedure SaveInFileClick(Sender: TObject);
    procedure FileMenuClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  MainForm: TMainForm;

implementation

{$R *.dfm}

Procedure TMainForm.Calculate(Num: Integer);
Var
    Comp, I: Integer;
Begin
    Comp:=1;
    for I := 2 to 2 * Num do
        if I mod 2 = 0 then
            Comp := Comp * I;
    Outputlabel.Caption := 'Произведение: ' + IntToStr(Comp);
End;

procedure TMainForm.CalculateButtonClick(Sender: TObject);
Var
    IsCorrect: Boolean;
begin
    IsCorrect := True;
    if ((StrToInt(InputNumber.Text) < 1) or (StrToInt(InputNumber.Text) > 9)) then
    begin
        IsCorrect := false;
        MessageDlg('Введите натуральное число в диапозоне от 1 до 9', mtError, [mbOk], 0);
    end;
    if (IsCorrect = true) then
    Begin
        Try
            Calculate(StrToInt(InputNumber.Text));
        Except
            MessageDlg('Введите натуральное число', mtError, [mbOk], 0);
        End;
    End;
end;

function CheckFile(Path: String): Boolean;
var
    FileToCheck: TextFile;
    N: Integer;
begin
    AssignFile(FileToCheck, Path);
    Reset(FileToCheck);
    CheckFile := true;
    try
        Readln(FileToCheck, N);
        if (N < 1) or (N > 9) then
            CheckFile := false;
    except
        CheckFile := false;
    end;
    CloseFile(FileToCheck);
end;

procedure TMainForm.OpenFileClick(Sender: TObject);
var
    InputFile: TextFile;
    N: Integer;
begin
    if OpenDialog.Execute then
    begin
        if CheckFile(OpenDialog.FileName) then
        begin
            AssignFile(InputFile, OpenDialog.FileName);
            Reset(InputFile);
            Read(InputFile, N);
            InputNumber.Text := IntToStr(N);
            CloseFile(InputFile);
            ShowMessage('Данные из файла успешно загружены');

        end
        else
            ShowMessage('Данные в файле некорректны');
    end;
end;

procedure TMainForm.FileMenuClick(Sender: TObject);
begin
    SaveInFile.Enabled := NOT (OutputLabel.Caption = '');
end;

procedure TMainForm.SaveInFileClick(Sender: TObject);
var
    OutputFile: TextFile;
begin
    if SaveDialog.Execute then
    begin
        AssignFile(OutputFile, SaveDialog.FileName);
        Rewrite(OutputFile);
        Write(OutputFile, MainForm.OutputLabel.Caption);
        CloseFile(OutputFile);
        ShowMessage('Успешно сохранено');
    end;
end;

end.