.net 当月的第一天和最后一天的方法

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// 使用的地方

//string firstDay; string lastDay;

//ReturnDateFormat(DateTime.Now.Month, out firstDay, out lastDay);

/// <summary>

/// 返回每月的第一天和最后一天
/// </summary>
/// <param name="month"></param>
/// <param name="firstDay"></param>
/// <param name="lastDay"></param>
public void ReturnDateFormat(int month, out string firstDay, out string lastDay)
{
int year = DateTime.Now.Year + month / 12;
if (month != 12)
{
month = month % 12;
}
switch (month)
{
case 1:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
break;
case 2:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
if (DateTime.IsLeapYear(DateTime.Now.Year))
lastDay = DateTime.Now.ToString(year + "-0" + month + "-29");
else
lastDay = DateTime.Now.ToString(year + "-0" + month + "-28");
break;
case 3:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString("yyyy-0" + month + "-31");
break;
case 4:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");
break;
case 5:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
break;
case 6:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");
break;
case 7:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
break;
case 8:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");
break;
case 9:
firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");
break;
case 10:
firstDay = DateTime.Now.ToString(year + "-" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-" + month + "-31");
break;
case 11:
firstDay = DateTime.Now.ToString(year + "-" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-" + month + "-30");
break;
default:
firstDay = DateTime.Now.ToString(year + "-" + month + "-01");
lastDay = DateTime.Now.ToString(year + "-" + month + "-31");
break;
}

}

// 相关链接：http://www.111cn.net/net/net/65534.htm

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