对“C#写的简单的日历，窗体输出。”的改写，精简了一半多代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace xianshirili
{
public class Calendar
{
public void PrintCalendar(int year, int month,TextBox textbox)
{
StringBuilder builder = new StringBuilder();
builder.Append(" 日 一 二 三 四 五 六\r\n");
int hawdays = GetWeeksOfDate(year, month, 1); //这个月的第一天星期几
int days = GetDaysOfMonth(year, month); //获取想要输出月份的天数

for (int i = 1; i <= hawdays * 3; i++) //打印第一排前面的空格
{
builder.Append(" ");
}
for (int j = 1; j <= days; j++)
{

if (j <= 9)
{
builder.Append(" ");
builder.Append(" ");
builder.Append(Convert.ToString(j));
}
// Console.Write(" {0}", j);

if (j >= 10)
{
builder.Append(" ");
builder.Append(Convert.ToString(j));
}
// Console.Write(" {0}", j);
if ((hawdays + j) % 7 == 0)
builder.Append("\r\n");
}

textbox.Text = builder.ToString();
}

// 计算当前日期以前的天数
public static int GetDaysOfDate(int year, int month, int day)
{
int days = 0;
for (int i = 1980; i < year; i++)
{
days += GetDaysOfYears(i);
}
for (int i = 1; i < month; i++)
{
days += GetDaysOfMonth(year, i);

}
days = days + day - 1;
return days;
}

//计算星期，返回具体的某一天星期几 值为0~6
public static int GetWeeksOfDate(int year, int month, int day)
{
int weeks = GetDaysOfDate(year, month, day);

return (weeks + 2) % 7;
}

// 判断是否闰年并返回当年总天数
public static bool LeapYear(int year)
{
return ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);
}

//判断月份，返回当月的天数
public static int GetDaysOfMonth(int year, int month)
{
int days = 30;
switch (month)
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days = 31; break;
case 4:
case 6:
case 9:
case 11:
days = 30; break;
case 2:
days = LeapYear(year) ? 29 : 28; break;
default:
days = 30; break;
}
return days;
}

//根据年，判断是否闰年并返回一年里有几天
public static int GetDaysOfYears(int year)
{
return LeapYear(year) ? 366 : 365;
}
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

public class Calendar
{
public void PrintCalendar(int year, int month, TextBox textbox)
{
StringBuilder builder = new StringBuilder();
builder.Append(" 日 一 二 三 四 五 六\r\n");
int hawdays = GetWeeksOfDate(year, month, 1); //这个月的第一天星期几
int days = GetDaysOfMonth(year, month); //获取想要输出月份的天数

for (int i = 1; i <= hawdays * 3; i++) //打印第一排前面的空格
{
builder.Append(" ");
}
for (int j = 1; j <= days; j++)
{
builder.Append(j.ToString().PadLeft(3, ' '));

if ((hawdays + j) % 7 == 0)
builder.Append("\r\n");
}
textbox.Text = builder.ToString();
}

//计算星期几: 星期日至星期六的值为0-6
public static int GetWeeksOfDate(int year, int month, int day)
{
DateTime dt = new DateTime(year, month, day);
DayOfWeek d = dt.DayOfWeek;
return Convert.ToInt32(d);
}
//获取指定年月的天数
public static int GetDaysOfMonth(int year, int month)
{
DateTime dtCur = new DateTime(year, month, 1);
int days = dtCur.AddMonths(1).AddDays(-1).Day;
return days;
}
}