c# string character replace

Question

I have a string where the third last character is sometimes a , If this is the case I want to replace it with a . The string could also have other

Answer 1

Try this

System.Text.RegularExpressions.Regex.Replace([the_string], "(,)(.{2})$", ".$2")

It should do it if by 'third last character' you literally mean the third-last character in the whole string.

That said - you might need to tweak if there are new lines - e.g. add the RegexOptions.Singleline enum as an extra parameter.

For better performance - probably - you could pre-declare the regex inside a class body:

static readonly Regex _rxReplace = new Regex("(,)(.{2})$", RegexOptions.Compiled);

Then when you want to use it it's just:

var fixed = _rxReplace.Replace([the_string], ".$2");