日期手动转汉字

目标效果：2020-12-22转化为——二零二零年十二月二十二日

private string DateToUpper(DateTime date)
{
    int year = date.Year;
    int month = date.Month;
    int day = date.Day;
    return MonthtoUpper(month) + "月" + DaytoUpper(day) + "日";
}

private string MonthtoUpper(int month)
{
    if (month < 10)
    {
        return NumtoUpper(month);
    }
    else
        if (month == 10) { return "十"; }

    else
    {
        return "十" + NumtoUpper(month - 10);
    }
}

private string DaytoUpper(int day)
{
    if (day < 20)
    {
        return MonthtoUpper(day);
    }
    else
    {
        String str = day.ToString();
        if (str[1] == '0')
        {
            return NumtoUpper(Convert.ToInt16(str[0].ToString())) + "十";
        }
        else
        {
            return NumtoUpper(Convert.ToInt16(str[0].ToString())) + "十"
                + NumtoUpper(Convert.ToInt16(str[1].ToString()));
        }
    }
}

private string NumtoUpper(int num)
{
    String str = num.ToString();
    string rstr = "";
    int n;
    for (int i = 0; i < str.Length; i++)
    {
        n = Convert.ToInt16(str[i].ToString());//char转数字,转换为字符串，再转数字
        switch (n)
        {
            case 0: rstr = rstr + "〇"; break;
            case 1: rstr = rstr + "一"; break;
            case 2: rstr = rstr + "二"; break;
            case 3: rstr = rstr + "三"; break;
            case 4: rstr = rstr + "四"; break;
            case 5: rstr = rstr + "五"; break;
            case 6: rstr = rstr + "六"; break;
            case 7: rstr = rstr + "七"; break;
            case 8: rstr = rstr + "八"; break;
            default: rstr = rstr + "九"; break;
        }
    }
    return rstr;
}