获取包含字符串的行号 [英] Get line number that contains a string

问题描述

如何获取文本文件中包含指定字符串的行号?

How to get a line number that contains a specified string in a text file?

示例文本文件包含:

红色
白
黄色
绿色

Red
White
Yellow
Green

如何获取黄色"行号?我可以在指定的行中写一个字符串，可以说我想在第二行中写一个字符串吗?

How to get "Yellow" line number? and can i write a string in a specified line, lets say i want to write a string in line 2?

推荐答案

要在文本文件中查找一行，您需要从文件开头读取各行，直到找到为止:

To find a line in a text file, you need to read the lines from the start of the file until you find it:

string fileName = "file.txt";
string someString = "Yellow";

string[] lines = File.ReadAllLines(fileName);
int found = -1;
for (int i = 0; i < lines.Length; i++) {
  if (lines[i].Contains(someString)) {
    found = i;
    break;
  }
}

如果要更改文件中的一行，则必须读取整个文件，然后将更改后的行写回去:

If you want to change a line in a file, you have to read the entire file and write it back with the changed line:

string[] lines = File.ReadAllLines(fileName);
lines[1] = "Black";
File.WriteAllLines(fileName, lines);

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