I need to replace the word PARAM_DATETIME in the string:

 string input = "^FT734,274^A0I,28,28^FH\\^FDPARAM_DATETIME^FS";

I'm trying with:

string newstr = Regex.Replace("^FT734,274^A0I,28,28^FH\\^FDPARAM_DATETIME^FS", @"\bPARAM_DATETIME\b", "27-01-2022");

but it doesn´t work.

The goal is to match the word PARAM_DATETIME even if it is preceded with F at the start of the word followed with any uppercase letter.

CodePudding user response：

If you only need to change the word PARAM_DATETIME, isn't it easier to use String.Replace?

string input = "^FT734,274^A0I,28,28^FH\\^FDPARAM_DATETIME^FS";
input = input.Replace("PARAM_DATETIME", "27-01-2022");

CodePudding user response：

You can use

Regex.Replace(text, @"\b(F[A-Z])?PARAM_DATETIME\b", "${1}27-01-2022")

See the regex demo. Details:

• \b - a word boundary
• (F[A-Z])? - Group 1 (optional): F and then any one ASCII uppercase letter
• PARAM_DATETIME - a word
• \b - a word boundary

The match is replaced with Group 1 value (${1}) and the hardcoded string.