C#（C sharp）字符串和时间的相互转换。
一、DateTime –> string
时间类型转化成字符串类型，那是相当的简单，直接调用ToString()方法即可。如：
DateTime dt = DateTime.Now;
string dtStr = dt.ToString();
如果想对输出格式化，可以这么写：
dt.ToString("yyyy年MM月dd日"); //2005年11月5日
dt.ToString("yyyy-MM-dd"); //2005-11-5
string.Format("{0:d}",dt); //2005-11-5
string.Format("{0:D}",dt); //2005年11月5日
时间类型格式化（成字符类型）可以通过两种方式：1、自定义时间格式。自己定义时间的构成和表示；2、标准时间格式。由标准库提供的有限的表示方式。（详细的情参考列表）
二、string -> DateTime
string dtString = “2009-10-12 00:12:05”;
DateTime dt = DateTime.Parse(dtStr); //方式一
DateTime dt2 = Convert.ToDateTime(dtStr); //方式二
当然DateTime也有多种表示方式（非格式化成字符串类型），如：
dt.ToFileTimeUtc(); //127756704859912816
dt.ToLocalTime(); //2005-11-5 21:21:25
dt.ToLongDateString(); //2005年11月5日
当然如果最后要打印出来，就需要ToString()一下，转化成字符串类型。
三、时间的其它方法，属性和运算
参考：
Custom DateTime Formatting
There are following custom format specifiers y (year), M (month), d (day), h (hour 12), H (hour 24), m (minute), s (second), f (second fraction), F (second fraction, trailing zeroes are trimmed), t (P.M or A.M) and z (time zone).
Following examples demonstrate how are the format specifiers rewritten to the output.
You can use also date separator / (slash) and time sepatator : (colon). These characters will be rewritten to characters defined in the current DateTimeFormatInfo.DateSeparator and DateTimeFormatInfo.TimeSeparator.
Here are some examples of custom date and time formatting:
[C#]
Standard DateTime Formatting
In DateTimeFormatInfo there are defined standard patterns for the current culture. For example property ShortTimePattern is string that contains value h:mm tt for en-US culture and value HH:mm for de-DE culture.
Following table shows patterns defined in DateTimeFormatInfo and their values for en-US culture. First column contains format specifiers for the String.Format method.
|
Specifier |
DateTimeFormatInfo property |
Pattern value (for en-US culture) |
|
|
t |
ShortTimePattern |
h:mm tt |
|
|
d |
ShortDatePattern |
M/d/yyyy |
|
|
T |
LongTimePattern |
h:mm:ss tt |
|
|
D |
LongDatePattern |
dddd, MMMM dd, yyyy |
|
|
f |
(combination of D and t) |
dddd, MMMM dd, yyyy h:mm tt |
|
|
F |
FullDateTimePattern |
dddd, MMMM dd, yyyy h:mm:ss tt |
|
|
g |
(combination of d and t) |
M/d/yyyy h:mm tt |
|
|
G |
(combination of d and T) |
M/d/yyyy h:mm:ss tt |
|
|
m, M |
MonthDayPattern |
MMMM dd |
|
|
y, Y |
YearMonthPattern |
MMMM, yyyy |
|
|
r, R |
RFC1123Pattern |
ddd, dd MMM yyyy HH':'mm':'ss 'GMT' (*) |
|
|
s |
SortableDateTimePattern |
yyyy'-'MM'-'dd'T'HH':'mm':'ss (*) |
|
|
u |
|