C# メモ

using System;
using System.Threading.Tasks;

public sealed class Timer
{
    private Action _action;
    private int _ms;
    private bool _setsTime;
    private bool _setsAction;
    private bool _excecuteStartAsyncBefore;

    public void SetTime(int ms)
    {
        CheckSetsTimeYet();
        _setsTime = true;
        _ms = ms;
    }

    public void SetAction(Action action)
    {
        CheckSetsActionYet();
        _setsAction = true;
        _action = action;
    }

    public async void StartAsync()
    {
        CheckReady();

        _excecuteStartAsyncBefore = true;
        await Task.Delay(_ms);
        Fire();
    }

    private void Fire()
    {
        _action.Invoke();
    }

    private void CheckReady()
    {
        CheckSetNeccesaryValues();
        CheckFirstExcecte();
    }

    private void CheckSetNeccesaryValues()
    {
        if (!_setsTime || !_setsAction)
            throw new Exception("Set Time and Action");
    }

    private void CheckFirstExcecte()
    {
        if (_excecuteStartAsyncBefore)
            throw new Exception("Not first execute");
    }

    private void CheckSetsTimeYet()
    {
        if (_setsTime)
            throw new Exception("Already Set Time");
    }

    private void CheckSetsActionYet()
    {
        if (_setsAction)
            throw new Exception("Already Set Action");
    }
}