C#输出格式为[00:00:00.00]的时分秒.毫秒

using UnityEngine;

public class TimeConvert : MonoBehaviour
{
    private float timeSpend = 0;
    private int hour;   //小时
    private int minute; //分钟
    private int second; //秒
    private int millisecond; //毫秒

    void Update()
    {
        timeSpend += Time.deltaTime;

        OnTimeConvert();

        Text();
    }

    public string OnTimeConvert()
    {
        hour = (int)timeSpend / 3600;
        minute = ((int)timeSpend - hour * 3600) / 60;
        second = (int)timeSpend - hour * 3600 - mi