Question

I want to find all alphanumeric characters between {{ and }} in a text.
Eg. if the text contain the substring {{foo}} I want to find foo.
If it contains {{#foo}} I want to find foo not #foo.

I have tried the following pattern (?<=\\{\\{)(.*?)(?=\\}\\}), but it always returns # in the second example above.

Can anyone help me?

Answer 1

You can try this:

(?<=\{\{[^A-Za-z0-9]*)([A-Za-z0-9]+)(?=.*\}\})

This expression lets you skip non-alphanumeric characters after {{ and before the first alphanumeric character, if any. It also lets you have non-alphanumerics preceding the closing }}.

EDIT

In response to your comment about f#oo: as far as I know, you cannot “glue together” multiple non-contiguous matched groups. The easiest solution is to use another regexp in your C# hosting program:

var rgx = new Regex(@"\W"); // Any non-word character
var result = rgx.Replace("f#oo$bar", ""); // Returns "foobar"

You would need to go back to your original regexp, because the one from the answer matches only the first contiguous block of alphanumerics.