什么是字符串格式C＃{0,12：N0}（结肠和昏迷） [英] what is String Format C# {0,12:N0} (colon and comas)

问题描述

这里是代码示例：

  string header = String.Format（{0，-12} {1， 8} {2,12} {1,8} {2,12} {3,14} \\\
，
城市，年份，人口 ; 
 Console.WriteLine（header）; 
 string output; 
 foreach（城市中的城市）{
 output = String.Format（{0，-12} {1,8：yyyy} {2,12：N0} {3,8：yyyy} {4,12：N0} {5,14：P1}，
 city.Item1，city.Item2，city.Item3，city.Item4，city.Item5，
（city.Item5  -  city .Item3）/（double）city.Item3）; 
 Console.WriteLine（output）; 
} 
} 
} 
 //示例显示以下输出：
 //城市年人口年人口变化（％）
 // 
 //洛杉矶1940 1,504,277 1950 1,970,358 31.0％
 //纽约1940 7,454,995 1950 7,891,957 5.9％
 //芝加哥1940 3,396,808 1950 3,620,962 6.6％
 //底特律1940 1,623,452 1950 1,849,568 13.9％
  

我理解了args后的冒号{0：N0}表示没有小数，昏迷怎么样？像{0，-12}和{1,12}在字符串格式的参数后coma是什么意思？

感谢

解决方案

MSDN文档是您的朋友（我在上面评论的链接不是最好的）：

复合格式

每个格式项采用以下形式，并由以下组件组成：
{index [，alignment] [：formatString]}

< blockquote>

所以 index 显然是所提供参数的索引：

  String.Format（Second argument = {1}，first argument = {0}，arg1，arg2）; 
  

顺便说一句， >

对齐指定了可变格式的索引，因为没有提供任何参数。所需的字段宽度和水平对齐方式：

如果对齐方式为正且左对齐，字段中的格式化数据为右对齐if对齐是否定的。

  String.Format（{0，-12} /第一个参数，左对齐，12个字符宽的列
{1,8：yyyy}+ //第二个参数，右对齐，8个字符宽的列，
 //格式化为年
{2,12：N0}+ //第三个参数，右对齐，12个字符宽的列，
 //格式化为数字，0个小数位
  
 
 
 
和 formatString 你已经知道了（例如数字（N）格式说明符）。
 
Okay here's the code example :
 string header = String.Format("{0,-12}{1,8}{2,12}{1,8}{2,12}{3,14}\n",
                                "City", "Year", "Population", "Change (%)");
  Console.WriteLine(header);
  string output;      
  foreach (var city in cities) {
     output = String.Format("{0,-12}{1,8:yyyy}{2,12:N0}{3,8:yyyy}{4,12:N0}{5,14:P1}",
                            city.Item1, city.Item2, city.Item3, city.Item4, city.Item5,
                            (city.Item5 - city.Item3)/ (double)city.Item3);
     Console.WriteLine(output);
  }
 }
}
// The example displays the following output:
//    City            Year  Population    Year  Population    Change (%)
//    
//    Los Angeles     1940   1,504,277    1950   1,970,358        31.0 %
//    New York        1940   7,454,995    1950   7,891,957         5.9 %
//    Chicago         1940   3,396,808    1950   3,620,962         6.6 %
//    Detroit         1940   1,623,452    1950   1,849,568        13.9 %
i understand about the colon after the args {0:N0} means no decimal, but what about the comas? like {0,-12}, and {1,12} what does coma means after the argument of the string format?

thanks
解决方案
MSDN Documentation is your friend (the link I gave in comments above wasn't the best either):

Composite Formatting  

  
Each format item takes the following form and consists of the following components:
  {index[,alignment][:formatString]}
So the index is obviously the index of the provided arguments:
String.Format("Second argument = {1}, first argument = {0}", arg1, arg2);
By the way, your header variable format indices are wrong, and unnecessary since no arguments are provided. 

Alignment specifies the desired width of the field and horizontal alignment:  

  
The formatted data in the field is right-aligned if alignment is positive and left-aligned if alignment is negative.


String.Format("{0,-12}" +    // first argument, left align, 12 character wide column
              "{1,8:yyyy}" + // second argument, right align, 8 character wide column,
                             // formatted as a year
              "{2,12:N0}" +  // third argument, right align, 12 character wide column,
                             // formatted as a number, 0 decimal places
And formatString you already know about (e.g. The Numeric ("N") Format Specifier).

                        
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