使用正则表达式在字符串中查找确切的字符

Question

I have strings like below

M10 end 
start M11
M1
M1 start
M n1
end M1

What I am trying to achieve is get the result having only " M1 " using regex.

This is my current code

Regex r = new Regex("^M1$|M1$");

The output looks like below which is missing string "M1 start"

M1
end M1

Answer 1

Regex r = new Regex("^.*\\bM1\\b.*$");

This should do it for you.See demo.Here \\b is word boundary which will match only M1 and not M10 .

\\b assert position at a word boundary (^\\w|\\w$|\\W\\w|\\w\\W)

https://regex101.com/r/sJ9gM7/113

Answer 2

Well, if you want not to overuse Regex, you can use

target="M1";
if( underTest.IndexOf(target) == 0 && underTest.Lenght == target.Lenght)
{
 ....
}

using a StringReader to split each line.