Only keep the legal chars in a text using a .NET Regex

Question

I have a list of legal characters and I want to remove all others chars from text.

// my legal chars. a-Z, numbers, space, _, - and percentage
string legalChars = "[\p{L}\p{Nd}_\- %]*"

string text = "[update], Text with {illegal} chars such as: !? {}";

I do find a lot of examples for removing illegal chars. I want to do the opposite.

Answer 1

How about:

String trimmed = Regex.Replace(input, @"[^\p{L}\p{Nd}_\- %]", "");

Or:

private static readonly Regex RemovalPattern 
   = new Regex(@"[^\p{L}\p{Nd}_\- %]");

...


string trimmed = RemovalPattern.Replace(input, "");

Note that your regex of legal characters currently doesn't include space, contrary to the comment.

Answer 2

Why not loop through the string yourselfa and check for each character if it's a legal char append the char to a new string (for example with stringbuilder)