C＃：DateTime - 经历一段时间？

Question

I have a period of days and I want to go through it and execute the same code on each date.

begin and end are DateTime format with difference of a month at least

while ( !(begin.Equals(end)) )
        {
           ...some code here...              
           begin = begin.AddDays(1);
        }

1. I'm not sure if it automatically upgrades the Month value when the Day value reaches the end of an exact month(in exact year) - for example February doesn't have always the same amount of days so...

2. Is there a better/shorter/nicer way of increasing the date by one day? For example something like this: begin.Day++ ; or this: begin++; ?

I'm not used to C# yet so sorry for asking this lame question and thank you in advance for any answer.

Answer 1

1) Yes it does. All date arithmetic is handled correctly for you.

2) Yes there is. You can do:

var oneDay = TimeSpan.FromDays(1);
...
begin += oneDay;

You could also use a for loop:

var oneDay = TimeSpan.FromDays(1);

for (DateTime currentDay = begin; currentDay < end; currentDay += oneDay)
{
    // Some code here.
}

One final thing: If you want to be sure to ignore the time component, you can ensure that the time part of the begin and end dates is set to midnight as follows:

begin = begin.Date;
end   = end.Date;

Make sure you have your bounds correct. The loop goes while currentDay < end - but you might need currentDay <= end if your time range is inclusive rather than exclusive.

Answer 2

Do it this way (don't compare for equality, because hours may be different and the loop goes forever).

    while ( begin <= end )
    {
       ...some code here...              
       begin = begin.AddDays(1);
    }

Answer 3

The code you've posted is correct and should work fine. And don't worry, the AddDays method will automatically increment the month and the year when necessarry.

You can also use a for loop if you find it more readable:

for (DateTime date = startDate; date < endDate; date = date.AddDays(1))
{
    // Your code here
}

Answer 4

You could try this, which I think is a little more succinct:

while (DateTime.Compare(begin, end) < 0)
{
    /* Some code here */
    begin = begin.AddDays(1);
}

The DateTime object knows how to increment months, years, etc. as appropriate, so you needn't worry about that.