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标题: C#string.Format()方法详细说明与教程 [打印本页]
作者: 站长苏飞    时间: 2013-8-16 11:21
标题: C#string.Format()方法详细说明与教程
              C#string.Format()方法详细说明与教程

    将指定字符串中的每个格式项替换为相应对象的值的文本等效项。                     
        
      
      重载此成员。有关此成员的完整信息（包括语法、用法和示例），请单击重载列表中的相应名称。


    Format(String, Object)            将指定字符串中的一个或多个格式项替换为指定对象的字符串表示形式。      

    Format(String, Object[])            将指定字符串中的格式项替换为指定数组中相应对象的字符串表示形式。      

    Format(IFormatProvider, String, Object[])            将指定字符串中的格式项替换为指定数组中相应对象的字符串表示形式。
  指定的参数提供区域性特定的格式设置信息。   

    Format(String, Object, Object)            将指定字符串中的格式项替换为两个指定对象的字符串表示形式。      

    Format(String, Object, Object, Object)            将指定字符串中的格式项替换为三个指定对象的字符串表示形式。   

                          每个重载的 Format 方法使用 复合格式设置功能，包括从零开始的索引的占位符称为格式项，
复合格式字符串中。              每个格式项都由参数数组中相应参数的字符串表示形式替换。

  如果参数值为 null，则其将替换为 String.Empty。  

例如，以下调用到 Format(String, Object, Object, Object) 方法包括一个格式字符串，
与三个格式项、{0}，{1}，{2} 和三个项目的参数列表。
[code=csharp]DateTime dat = new DateTime(2012, 1, 17, 9, 30, 0);
string city = "Chicago";
int temp = -16;
string output = String.Format("At {0} in {1}, the temperature was {2} degrees.",
                              dat, city, temp);
Console.WriteLine(output);
// The example displays the following output:
//    At 1/17/2012 9:30:00 AM in Chicago, the temperature was -16 degrees.   [/code]
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+0011.20E+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
                        
StringsThere 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 <-
NumbersBasic 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}1.42System.
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}
1500.4200Pads 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.
e
Exponent placeholder
{0:00e+0}
15e+2Many 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:
DatesNote 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 date10/12/2002
D
Long dateDecember 10, 2002
t
Short time10:11 PM
T
Long time10:11:29 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 & time10/12/2002 10:11 PM
G
Default date & time (long)10/12/2002 10:11:29 PM
M
Month day patternDecember 10
r
RFC1123 date stringTue, 10 Dec 2002 22:11:29 GMT
s
Sortable date string2002-12-10T22:11:29
u
Universal sortable, local time2002-12-10 22:13:50Z
U
Universal sortable, GMTDecember 11, 2002 3:13:50 AM
Y
Year month patternDecember, 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 ExamplesString.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%
                        
更详细的大家可以上MSDN查阅
http://msdn.microsoft.com/zh-cn/library/system.string.format.aspx





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