用正则表达式替换字符串

Question

Suppose that I have a text like "Hello @c1, please go here and play with @c12, @c1 goes and plays", I would like to write a pattern to replace all of @c1 with some value but in the same time the regular expression must not change @c12 or @c123 etc.. it should replace only the matched string. I have been trying for hours, but failing to produce the right output, so can anyone can help me with what to do regarding it with articles or code samples

I am using .Net Framework for writing the Regular expression

Answer 1

You can use this regex:

@c1\b

Working demo

The idea is to use a word boundary after your text and that would solve your problem

Answer 2

You can either use a word boundary \\b or Negative Lookahead here.

A word boundary asserts that on one side there is a word character, and on the other side there is not.

String s = "Hello @c1, please go play with @c12 and @c123";
String r = Regex.Replace(s, @"@c1\b", "foo");
Console.WriteLine(r); //=> "Hello foo, please go play with @c12 and @c123"

Negative Lookahead asserts that at that position in the string, what immediately follows is not a digit.

String s = "Hello @c1, please go play with @c12 and @c123";
String r = Regex.Replace(s, @"@c1(?!\d)", "foo");
Console.WriteLine(r); //=> "Hello foo, please go play with @c12 and @c123"

Answer 3

@c1(?![a-zA-Z0-9])

您可以使用负前瞻进行此操作

Answer 4

You could use a lookahead and lookbehind,

(?<=\W|^)@c1(?=\W|$)

Code:

string str = "Hello @c1, please go here and play with @c12, @c1 goes and plays";
string result = Regex.Replace(str, @"(?<=\W|^)@c1(?=\W|$)", "foo");
Console.WriteLine(result);
Console.ReadLine();

IDEONE

Answer 5

Try this pattern:

@c(?=1\D)1

Demo