Regex expression to bold using asterisks - regex

Question

I have a question regarding using a regular expression to bold text within a string using asterisks.
The other questions on this topic work well for simple scenarios however we have encountered some issues.
Our particular scenario is for asterisks to be replaced with <bold></bold> tags.
It must also be able to handle multiple asterisks as well as an uneven number of asterisks.
Our example input text is as follows;
string exampleText1 = "**** PLEASE NOTE *** Testing, *nuts*, **please note..., test";
string exampleText2 = "**Test text (10)";
Our current regex is as follows;
Regex _boldRegex = new Regex(#"(\*)+([^*?$]+)+(\*)");
string value = _boldRegex.Replace(exampleText1, #"<bold>$2</bold>");
Example 1 should show "<bold> PLEASE NOTE </bold> Testing, <bold>nuts</bold>, *please note..., test" where the groups of asterisks are treated as single asterisks and an unfinished tag is ignored.
Example 2 crashes the program because it expects a 'closing' asterisk. It should show "*Text text (10)"
Can anyone help by suggesting a new regex, bearing in mind the ability to handle groups of asterisks and also an uneven number of asterisks?
Thanks in advance.

Answer 1

For you examle data, you might use an optional part with a capture group to capture the repeated character class without newlines between 1 or more *
In the callback of replace, you can test for the existence of group 1, and do the replacements based on that.
\*+(?:([^*?$\n\r]+)\*+)?
The pattern matches:
\*+ Match 1+ times *
(?: Non capture group
( Capture group 1
[^*?$\n\r]+ Match 1+ times any char other than the listed in the character class
) Close group 1
\*+ Match 1+ times *
)? Close on capture group
See a regex demo.
For example
Regex _boldRegex = new Regex(#"\*+(?:([^*?$\n\r]+)\*+)?");
string exampleText1 = #"**** PLEASE NOTE *** Testing, *nuts*, **please note..., test
**Test text (10)";
string value = _boldRegex.Replace(exampleText1, m =>
m.Groups[1].Success ? String.Format("<bold>{0}</bold>", m.Groups[1].Value) : "*"
);
Console.WriteLine(value);
Output
<bold> PLEASE NOTE </bold> Testing, <bold>nuts</bold>, *please note..., test
*Test text (10)