Using Regex to replace a specific string occurrence but ignore others based on neighboring characters

I have a string

   "sub section 15(1) of main section, this might be a <link href="15(1)">15(1)</link>". 

I want to use the Regex.Replace method to replace "15(1)" with a new string value of "15" but only where it occurs individually.

I am using the following pattern but it's not working.

 temp = "sub section 15(1) of main section, this might be a <link href="15(1)">15(1)</link>";    
 temp = Regex.Replace(temp, @"15(1)", @"15");

The output string should be:

"开发者_如何学Gosub section 15 of main section, this might be a <link href="15(1)">15(1)</link>"

Any help will be appreciated.

Thanks

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In your post you said you want to replace "15(1)" when it is "used individually." Does that mean when it is surrounded by whitespace?

This approach matches your desired output:

string pattern = @"(?<=^|\s)15\(1\)(?=\s|$)";
string result = Regex.Replace(input, pattern, "15");
Console.WriteLine(result);

This pattern will match only if the value occurs at the start of the line or is preceded by a whitespace character, and if it is followed by a whitespace character or the end of the line.

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Try this (note you need to escape the brackets around 1):

\W15\(1\)\W

where \W is a non-word character; or

\s15\(1\)\s

where \s is a whitespace character.

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This works (?<!\S)15\(1\)(?!\S)