/// <summary>
/// 比较两个日期大小
/// </summary>
/// <param name="dateStr1">日期1</param>
/// <param name="dateStr2">日期2</param>
/// <param name="msg">返回信息</param>
public void CompanyDate(string dateStr1, string dateStr2,ref string msg) {
//将日期字符串转换为日期对象
DateTime t1 = Convert.ToDateTime(dateStr1);
DateTime t2 = Convert.ToDateTime(dateStr2);
//通过DateTIme.Compare()进行比较（）
int compNum = DateTime.Compare(t1, t2);
//t1> t2
if (compNum > 0) {
msg = "t1:(" + dateStr1 + ")大于" + "t2(" + dateStr2 + ")";
}
//t1= t2
if (compNum == 0) {
msg = "t1:(" + dateStr1 + ")等于" + "t2(" + dateStr2 + ")";
}
//t1< t2
if (compNum < 0) {
msg = "t1:(" + dateStr1 + ")小于" + "t2(" + dateStr2 + ")";
}
}