Regex replace multiple groups

Question

I would like to use regular expressions to replace multiple groups with corresponding replacement string.

Replacement table:

• \"&\" ->

Answer 1

Given a dictionary that defines your replacements:

IDictionary map = new Dictionary()
{
    {"&","__amp"},
    {"#","__hsh"},
    {"1","5"},
    {"5","6"},
};

You can use this both for constructing a Regular Expression, and to form a replacement for each match:

var str = "a1asda&fj#ahdk5adfls";
var regex = new Regex(String.Join("|",map.Keys));
var newStr = regex.Replace(str, m => map[m.Value]);
// newStr = a5asda__ampfj__hshahdk6adfls

Live example: http://rextester.com/rundotnet?code=ADDN57626

This uses a Regex.Replace overload which allows you to specify a lambda expression for the replacement.

---

It has been pointed out in the comments that a find pattern which has regex syntax in it will not work as expected. This could be overcome by using Regex.Escape and a minor change to the code above:

var str = "a1asda&fj#ahdk5adfls";
var regex = new Regex(String.Join("|",map.Keys.Select(k => Regex.Escape(k))));
var newStr = regex.Replace(str, m => map[m.Value]);
// newStr = a5asda__ampfj__hshahdk6adfls