c# ToString() 格式化字符串、C# String.Format格式说明 http://linglong117.blog.163.com/blog/static/2771454720

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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

货币

2.5.ToString("C")

￥2.50

十进制数

25.ToString("D5")

00025

科学型

25000.ToString("E")

2.500000E+005

固定点

25.ToString("F2")

25.00

常规

2.5.ToString("G")

2.5

数字

2500000.ToString("N")

2,500,000.00

十六进制

255.ToString("X")

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)＄2.000D十进制string.Format("{0:D3}", 2)002E科学计数法1.20E+0011.20E+001G常规string.Format("{0:G}", 2)2N用分号隔开的数字string.Format("{0:N}", 250000)250,000.00X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.

SampleGeneratesString.Format("-<{1,10}<-", "Hello");-< Hello<-String.Format("-<{1,-10}<-", "Hello");-<Hello <-

Numbers

Basic number formatting specifiers:

SpecifierTypeFormat

Output
(Passed
Double 1.42)

Output
(Passed
Int -12400)

cCurrency{0:c}＄1.42-＄12,400dDecimal (Whole number){0:d}System.
FormatException-12400eScientific{0:e}1.420000e+000-1.240000e+004fFixed point{0:f}1.42-12400.00gGeneral{0:g}1.42-12400nNumber with commas for thousands{0:n}1.42-12,400rRound trippable{0:r}1.42System.
FormatExceptionxHexadecimal{0:x4}System.
FormatExceptioncf90

Custom number formatting:

SpecifierTypeExampleOutput (Passed Double 1500.42)Note0Zero placeholder{0:00.0000}1500.4200Pads with zeroes.#Digit placeholder{0:(#).##}(1500).42 .Decimal point{0:0.0}1500.4 ,Thousand separator{0:0,0}1,500Must be between two zeroes.,.Number scaling{0:0,.}2Comma adjacent to Period scales by 1000.%Percent{0:0%}150042%Multiplies by 100, adds % sign.eExponent placeholder{0:00e+0}15e+2Many exponent formats available.;Group separatorsee 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.

SpecifierTypeExample (Passed System.DateTime.Now)dShort date10/12/2002DLong dateDecember 10, 2002tShort time10:11 PMTLong time10:11:29 PMfFull date & timeDecember 10, 2002 10:11 PMFFull date & time (long)December 10, 2002 10:11:29 PMgDefault date & time10/12/2002 10:11 PMGDefault date & time (long)10/12/2002 10:11:29 PMMMonth day patternDecember 10rRFC1123 date stringTue, 10 Dec 2002 22:11:29 GMTsSortable date string2002-12-10T22:11:29uUniversal sortable, local time2002-12-10 22:13:50ZUUniversal sortable, GMTDecember 11, 2002 3:13:50 AMYYear month patternDecember, 2002

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

Custom date formatting:

SpecifierTypeExampleExample OutputddDay{0:dd}10dddDay name{0:ddd}TueddddFull day name{0:dddd}Tuesdayf, ff, ...Second fractions{0:fff}932gg, ...Era{0:gg}A.D.hh2 digit hour{0:hh}10HH2 digit hour, 24hr format{0:HH}22mmMinute 00-59{0:mm}38MMMonth 01-12{0:MM}12MMMMonth abbreviation{0:MMM}DecMMMMFull month name{0:MMMM}DecemberssSeconds 00-59{0:ss}46ttAM or PM{0:tt}PMyyYear, 2 digits{0:yy}02yyyyYear{0:yyyy}2002zzTimezone offset, 2 digits{0:zz}-05zzzFull timezone offset{0:zzz}-05:00:Separator{0:hh:mm:ss}10:43:20/Separator{0:dd/MM/yyyy}10/12/2002

Enumerations

SpecifierTypegDefault (Flag names if available, otherwise decimal)fFlags alwaysdInteger alwaysxEight 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".

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