c# ToString() 格式化字符串 、C# String.Format格式说明

格式化数值：有时，我们可能需要将数值以一定的格式来呈现，就需要对数值进行格式化。我们使用格式字符串指定格式。格式字符串采用以下形式：Axx，其中 A 为格式说明符，指定格式化类型，xx 为精度说明符，控制格式化输出的有效位数或小数位数。

格式说明符	说明	示例	输出
C	货币	2.5.ToString("C")	￥2.50
D	十进制数	25.ToString("D5")	00025
E	科学型	25000.ToString("E")	2.500000E+005
F	固定点	25.ToString("F2")	25.00
G	常规	2.5.ToString("G")	2.5
N	数字	2500000.ToString("N")	2,500,000.00
X	十六进制	255.ToString("X")	FF

     

C# ToString固定长度一个数值可用如下方法： 

例如i=1； 
i.ToString().PadLeft(10,'0'); 
固定长度为10，左不足补0，结果为0000000001； 

i=1； 
i.ToString("N").PadLeft(10,'0'); 
结果为00000001.00； 

i=1； 
i.ToString().PadLeft(10,' '); 
结果为 1；

C#格式化数值结果表

字符	说明	示例	输出
C	货币	string.Format("{0:C3}", 2)	＄2.000
D	十进制	string.Format("{0:D3}", 2)	002
E	科学计数法	1.20E+001	1.20E+001
G	常规	string.Format("{0:G}", 2)	2
N	用分号隔开的数字	string.Format("{0:N}", 250000)	250,000.00
X	十六进制	string.Format("{0:X000}", 12)	C
		string.Format("{0:000.000}", 12.2)	012.200

Strings

There really isn't any formatting within a strong, beyond it's alignment. Alignment works for any argument being printed in a String.Format call.

 

Sample	Generates
String.Format("->{1,10}<-", "Hello");	-> Hello<-
String.Format("->{1,-10}<-", "Hello");	->Hello <-

Numbers

Basic number formatting specifiers:

 

Specifier	Type	Format	Output  (Passed  Double 1.42)	Output  (Passed  Int -12400)
c	Currency	{0:c}	＄1.42	-＄12,400
d	Decimal (Whole number)	{0:d}	System. FormatException	-12400
e	Scientific	{0:e}	1.420000e+000	-1.240000e+004
f	Fixed point	{0:f}	1.42	-12400.00
g	General	{0:g}	1.42	-12400
n	Number with commas for thousands	{0:n}	1.42	-12,400
r	Round trippable	{0:r}	1.42	System. FormatException
x	Hexadecimal	{0:x4}	System. FormatException	cf90

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 "[phone]".

 

变量.ToString()

字符型转换 转为字符串 
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进制) 
12345.ToString("p"); //生成 1,234,500.00%

C#中ToString格式大全

C	货币	2.5.ToString("C")	￥2.50
D	十进制数	25.ToString("D5")	00025
E	科学型	25000.ToString("E")	2.500000E+005
F	固定点	25.ToString("F2")	25.00
G	常规	2.5.ToString("G")	2.5
N	数字	2500000.ToString("N")	2,500,000.00
X	十六进制	255.ToString("X")	FF

formatCode 是可选的格式化代码字符串。（详细内容请搜索“格式化字符串”查看）

必须用“{”和“}”将格式与其他字符分开。如果恰好在格式中也要使用大括号，可以用连续的两个大括号表示一个大括号，即： “{{”或者“}}”。

常用格式举例：

（1） int i=12345;

this.textBox1.Text=i.ToString();

//结果 12345（this指当前对象，或叫当前类的实例）

this.textBox2.Text=i.ToString("d8");

//结果 00012345

（2） int i=123;

double j=123.45;

string s1=string.Format("the value is {0,7:d}",i);

string s2=string.Format("the value is {0,7:f3}",j);

this.textBox1.Text=s1 ;

//结果 the value is 123

this.textBox2.Text=s2;

//结果 the value is 123.450

（3）double i=12345.6789;

this.textBox1.Text=i.ToString("f2"); //结果 12345.68

this.textBox2.Text=i.ToString("f6");

//结果 12345.678900

（4）double i=12345.6789;

this.textBox1.Text=i.ToString("n"); //结果 12,345.68

this.textBox2.Text=i.ToString(“n4”); //结果 12,345.6789

（5）double i=0.126;

string s=string.Format("the value is {0:p}",i);

this.textBox1.Text=i.ToString("p"); //结果 12.6%

this.textBox2.Text=s; //结果 the value is 12.6%

（6） DateTime dt =new DateTime(2003,5,25);

this.textBox1.Text=dt.ToString("yy.M.d");

//结果 03.5.25

this.textBox2.Text=dt.ToString(“yyyy年M月”);

//结果 2003年5月

Convert.ToDateTime("2005/12/22 22:22:22").ToString("yyyy/MM/dd HH:mm:ss")
"2005/12/22 22:22:22"

（7） int i=123;

double j=123.45;

string s=string.Format("i:{0,-7},j:{1,7}",i,j);

//-7表示左对齐，占7位

this.textBox1.Text=s ;

//结果i:123 ,j: 123.45