C# 检查 DateTime 是否在 DateTime.Now 之前
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Checking if a DateTime is before DateTime.Now
提问by Newbie
How can I check using some form of ifstatement if a certain DateTime, (say in this case called dateAndTime1) is before the current date and time, which I presume will be retrieved using DateTime.Now?
if如果某个DateTime,（在这种情况下称为 dateAndTime1）在当前日期和时间之前（我认为将使用 检索），我如何使用某种形式的语句进行检查DateTime.Now？
采纳答案by Jim
if(dateAndTime1 < DateTime.Now)
{
//do something
}
回答by welegan
the <, <=, >, >= and == operators work on DateTime instances, so
<、<=、>、>= 和 == 运算符适用于 DateTime 实例，因此
if(dateAndTime1 < DateTime.Now)
if(dateAndTime1 < DateTime.Now)
Note that if you are comparing this in a loop, some small efficiency can be gained by setting DateTime now = DateTime.Nowbefore the loop and comparing against now
请注意，如果您在循环中进行比较，则可以通过DateTime now = DateTime.Now在循环前进行设置并与now
回答by Chase Florell
Inline works too.
内联也有效。
// bool variable
bool isHistory = dateAndTime1 < DateTime.Now;
// string return statement
return dateAndTime1 < DateTime.Now ? "History" : "Future";
