如何将一部分字符串复制到另一个字符串中 [英] how to copy a part of string into another string

问题描述

我正在尝试使用此代码复制包含年份的字符串的最后一部分...

所以我可以计算年龄...





string DOB =10/10/1992

string Year =;

int j = 0;

for（int i = 5; i< 10; i ++）

{

year [j] = DOB [i]; //错误

j ++;

}

解决方案

不 - 你做不到因为字符串是 immutable ，它会测量一旦创建了一个字符串，就无法以任何方式更改它。如果要提取字符串的一部分，则需要从现有字符串中创建一个新字符串：

  string  DOB =   10/10/1992; 
  string  year = DOB.Substring（ 6 ， 4 ）; 
 

或者更好，将日期解析为DateTime，然后从中得到年份：

  string  DOB =   10/10/1992 ; 
 DateTime dob = DateTime.Parse（DOB）; 
  string  year = dob.Year.ToString（）; 
 

当用户输入日期时，它可以更灵活地工作，因为它处理的日期格式比明确的子字符串更多。

  string  DOB =   10/10/1992  
 datetime DOB = datetime.parse（dob.tostring（））; 
 
  int  year = DOB.year; 

 Year = DOB.Split（'  /'）。Last（）; 

i'm trying this code to copy last part on string which contain year...
so i would be able to calculat age from this...


string DOB = "10/10/1992"
string Year = "";
int j=0;
for(int i = 5 ; i < 10 ; i ++)
{
year[j]=DOB[i];// error
j++;
}

解决方案

No - you can't do that, because strings are immutable, which measn that once a string has been created, you cannot change it in any way. If you want to extract part of a string, then you need to create a new string from the existing one:

string DOB = "10/10/1992";
string year = DOB.Substring(6, 4);

Or better, parse the date into a DateTime, and then get the year from that:

string DOB = "10/10/1992";
DateTime dob = DateTime.Parse(DOB);
string year = dob.Year.ToString();

This works more flexibly, when the user can enter dates as it copes with more date formats than an explicit substring.

string DOB = "10/10/1992"
datetime DOB= datetime.parse(dob.tostring());

int year=DOB.year;

Year = DOB.Split('/').Last();

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