C# Programming :: Regex - dynamically creating pattern issue


	Regex - dynamically creating pattern issue I'm trying to use Regex.Replace to replace a single word in a string, but I have to pass in the string. It won't ever match, but if I hard- code the word it works fine. Please help!! string stringToAlter = "ab cd ef gh"; // --- Pattern entered as string works fine string pat1 = @"\bcd\b"; string newStg1 = Regex.Replace(stringToAlter, @pat1, "xxx"); WriteLine("first try = " + newStg1); // --- But passing in the word and concatenating doesn't! string pat2 = @"\b" + "cd" + "\b"; newStg1 = Regex.Replace(stringToAlter, @pat2, "xxx"); WriteLine("second try = " + newStg1); results: first try = ab xxx ef gh second try = ab cd ef gh On Mar 23, 8:54 pm, "Deanna" <ddelapa@gmail.com> wrote: - Hide quoted text - > I'm trying to use Regex.Replace to replace a single word in a string, > but I have to pass in the string. It won't ever match, but if I hard- > code the word it works fine. Please help!! > string stringToAlter = "ab cd ef gh"; > // --- Pattern entered as string works fine > string pat1 = @"\bcd\b"; > string newStg1 = Regex.Replace(stringToAlter, @pat1, "xxx"); > WriteLine("first try = " + newStg1); > // --- But passing in the word and concatenating doesn't! > string pat2 = @"\b" + "cd" + "\b"; > newStg1 = Regex.Replace(stringToAlter, @pat2, "xxx"); > WriteLine("second try = " + newStg1); > results: > first try = ab xxx ef gh > second try = ab cd ef gh You neglected to add the '@' to the second "\b" in your pattern. It should be... string pat2 = @"\b" + "cd" + @"\b"; Also, I could be wrong, but isn't the '@' unnecessary when accessing the variable? - Hide quoted text - > newStg1 = Regex.Replace(stringToAlter, @pat2, "xxx"); Deanna wrote: > I'm trying to use Regex.Replace to replace a single word in a string, > but I have to pass in the string. It won't ever match, but if I hard- > code the word it works fine. Please help!! > string stringToAlter = "ab cd ef gh"; > // --- Pattern entered as string works fine > string pat1 = @"\bcd\b"; > string newStg1 = Regex.Replace(stringToAlter, @pat1, "xxx"); > WriteLine("first try = " + newStg1); > // --- But passing in the word and concatenating doesn't! > string pat2 = @"\b" + "cd" + "\b"; Change "\b" to @"\b". > newStg1 = Regex.Replace(stringToAlter, @pat2, "xxx"); > WriteLine("second try = " + newStg1); > results: > first try = ab xxx ef gh > second try = ab cd ef gh If the string might contain characters that have any special meaning in a regular expression, use the Regex.Escape method on when creating the pattern. -- Gran Andersson _____ http://www.guffa.com -----------------------------------------------Reply----------------------------------------------- Yota wrote: > Also, I could be wrong, but isn't the '@' unnecessary when accessing > the variable? >> newStg1 = Regex.Replace(stringToAlter, @pat2, "xxx"); Correct. It can be used if you need to use a keyword as variable name, like @class, but I have yet to see any situation where this really would be needed. -- Gran Andersson _____ http://www.guffa.com