C＃错误“字符串未被识别为有效的DateTime”

Question

I am trying to save the DateTime.Now in the format "yyyyMMdd"

I have this code

string todaysDate = DateTime.Now.ToString();

...

U_Date_of_PD_added = GetDateFromString(todaysDate) 

// U_Date_of_PD_added is a datetime Database field

...

//Method to get date from string
private DateTime GetDateFromString(string dateString)
{
   string format = "yyyyMMdd";
   return DateTime.ParseExact(dateString, format, CultureInfo.InvariantCulture);
}

I keep getting the error "String was not recognized as a valid DateTime." as it tries to parse. What could be wrong?

I do not care if it saves the time, I would prefer 00:00:00.000

Answer 1

将日期转换为字符串时，还需要提供格式字符串：

string todaysDate = DateTime.Now.ToString("yyyyMMdd", CultureInfo.InvariantCulture);

Answer 2

First you get today's date and then convert in string as follow and you are done.

DateTime today = DateTime.Today.Date;
string date = today.ToString("yyyy/MM/dd");

Answer 3

DateTime.Now.ToString("yyyyMMdd", CultureInfo.InvariantCulture);

will give you the current date. Note that it's important the CultureInfo.InvariantCulture . If you don't trust it, try:

var r = DateTime.Now.ToString("yyyyMMdd", new CultureInfo("ar-SA")); // 14321128
var r2 = DateTime.Now.ToString("yyyyMMdd", CultureInfo.InvariantCulture); // 20111026

Answer 4

DateTime.Now.ToString() results in a format that is region specific, but it mostly contains the time. This format is called "General date/time pattern (long time)."

So trying to parse it with your format string will fail because your format string does not contain information about the time component.

You can use DateTime.TryParse without providing a format string or you have to provide your format string to your call to DateTime.Now.ToString as well.

Answer 5

The value of todaysDate cannot be converted to a DateTime object by using DateTime.Now.ToString() because DateTime.Now.ToString() results in a value that uses the default date format ( 26-10-2011 14:02:31 ). Try doing this instead: string todaysDate = DateTime.Now.ToString("yyyyMMdd"); and you should be able to convert it back using your GetDateFromString method.

Answer 6

DateTime.Now.ToString("yyyyMMdd")将返回20110926的字符串。