How to Regex search/replace only first occurrence in a string in .NET?

Question

It seems the .NET Regex.Replace method automatically replaces all matching occurrences. I could provide a MatchEvaluator delegate that returns the matched string after the

Answer 1

In that case you can't use:

string str ="abc546_$defg";
str = Regex.Replace(str,"[^A-Za-z0-9]", "");

Instead you need to declare new Regex instance and use it like this:

string str ="abc546_$defg";
Regex regx = new Regex("[^A-Za-z0-9]");
str = regx.Replace(str,"",1)

Notice the 1, It represents the number of occurrences the replacement should occur.