很多類都重寫了ToString方法， 導致很多類的tostring到底執行了什么，有哪些參數，都不清楚。。。。很郁悶！
對于int，double等的tostring：

C ?	? 貨幣 ?	? 2.5.ToString("C") ?	? ￥2.50 ?
? D ?	? 十進制數 ?	? 25.ToString("D5") ?	? 00025 ?
? E ?	? 科學型 ?	? 25000.ToString("E") ?	? 2.500000E+005 ?
? F ?	? 固定點 ?	? 25.ToString("F2") ?	? 25.00 ?
? G ?	? 常規 ?	? 2.5.ToString("G") ?	? 2.5 ?
? N ?	? 數字 ?	? 2500000.ToString("N") ?	? 2,500,000.00 ?
? X ?	? 十六進制 ?	? 255.ToString("X") ?	? FF

格式符	應?用	含?義	示?例
C	數字類型	專用場合的貨幣值	$4834.50 (USA) ￡4834.50 (UK)
D	只用于整數類型	一般的整數	4834
E	數字類型	科學計數法	4.834E+003
F	數字類型	小數點后的位數固定	4384.50
G	數字類型	一般的數字	4384.5
N	數字類型	通常是專用場合的數字 格式	4,384.50 (UK/USA) 4 384,50 (歐洲大陸)
P	數字類型	百分比計數法	432,000.00%
X	只用于整數類型	16進制格式	1120 (如果要顯示0x1120，需要寫上0x)

Custom number formatting:

?

Specifier	Type	Example	Output (Passed Double 1500.42)	Note
0	Zero placeholder	{0:00.0000}	1500.4200	Pads with zeroes.
#	Digit placeholder	{0:(#).##}	(1500).42
.	Decimal point	{0:0.0}	1500.4
,	Thousand separator	{0:0,0}	1,500	Must be between two zeroes.
,.	Number scaling	{0:0,.}	2	Comma adjacent to Period scales by 1000.
%	Percent	{0:0%}	150042%	Multiplies by 100, adds % sign.
e	Exponent placeholder	{0:00e+0}	15e+2	Many exponent formats available.
;	Group separator	see below		?

The group separator is especially useful for formatting currency values which require that negative values be enclosed in parentheses. This currency formatting example at the bottom of this document makes it obvious:

Dates

Note that date formatting is especially dependant on the system's regional settings; the example strings here are from my local locale.

?

Specifier	Type	Example (Passed System.DateTime.Now)
d	Short date	10/12/2002
D	Long date	December 10, 2002
t	Short time	10:11 PM
T	Long time	10:11:29 PM
f	Full date & time	December 10, 2002 10:11 PM
F	Full date & time (long)	December 10, 2002 10:11:29 PM
g	Default date & time	10/12/2002 10:11 PM
G	Default date & time (long)	10/12/2002 10:11:29 PM
M	Month day pattern	December 10
r	RFC1123 date string	Tue, 10 Dec 2002 22:11:29 GMT
s	Sortable date string	2002-12-10T22:11:29
u	Universal sortable, local time	2002-12-10 22:13:50Z
U	Universal sortable, GMT	December 11, 2002 3:13:50 AM
Y	Year month pattern	December, 2002

The 'U' specifier seems broken; that string certainly isn't sortable.

Custom date formatting:

?

Specifier	Type	Example	Example Output
dd	Day	{0:dd}	10
ddd	Day name	{0:ddd}	Tue
dddd	Full day name	{0:dddd}	Tuesday
f, ff, ...	Second fractions	{0:fff}	932
gg, ...	Era	{0:gg}	A.D.
hh	2 digit hour	{0:hh}	10
HH	2 digit hour, 24hr format	{0:HH}	22
mm	Minute 00-59	{0:mm}	38
MM	Month 01-12	{0:MM}	12
MMM	Month abbreviation	{0:MMM}	Dec
MMMM	Full month name	{0:MMMM}	December
ss	Seconds 00-59	{0:ss}	46
tt	AM or PM	{0:tt}	PM
yy	Year, 2 digits	{0:yy}	02
yyyy	Year	{0:yyyy}	2002
zz	Timezone offset, 2 digits	{0:zz}	-05
zzz	Full timezone offset	{0:zzz}	-05:00
:	Separator	{0:hh:mm:ss}	10:43:20
/	Separator	{0:dd/MM/yyyy}	10/12/2002

Enumerations

?

Specifier	Type
g	Default (Flag names if available, otherwise decimal)
f	Flags always
d	Integer always
x	Eight digit hex.

Some Useful Examples

String.Format("{0:$#,##0.00;($#,##0.00);Zero}", value);

This will output "$1,240.00" if passed 1243.50. It will output the same format but in parentheses if the number is negative, and will output the string "Zero" if the number is zero.

String.Format("{0:(###) ###-####}", 18005551212);

This will output "(800) 555-1212".

?

變量.ToString()

字符型轉換 轉為字符串
12345.ToString("n"); //生成 12,345.00
12345.ToString("C"); //生成 ￥12,345.00
12345.ToString("e"); //生成 1.234500e+004
12345.ToString("f4"); //生成 12345.0000
12345.ToString("x"); //生成 3039 (16進制)
12345.ToString("p"); //生成 1,234,500.00%

轉載于:https://www.cnblogs.com/jacktu/archive/2007/11/30/978293.html

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