正则表达式在 { } 之间匹配，但不是 {{ }}

Question

I'm trying to match what's between 2 curly braces, but ignore scenarios with double/escape curly braces, ie "This is {match}, this is a {{non-match}}." which should just match "match". I've tried:

var regex = new Regex("{{1}(.*?)}{1}");

but it's too greedy

Answer 1

You could take advantage of lookaheads/lookbehinds within a regular expression to match only content that occurs within a single set of curly braces with this expression:

(?<!{){([^{}]+)}(?!})

There's probably a bit of room for optimization, but it should accomplish what you are looking to achieve.

Explanation

// This looks for an opening curly brace that isn't preceded by another one
(?<!{){
// This is your capturing group that matches one or more non-curly brace characters
([^{}]+)
// This looks for a closing curly brace that isn't followed by another
}(?!})

Example

You can see an interactive example here and the related code demonstrated below which only returns the expected value from your single sets of quotes:

var example = "This is a {match} but this {{is not a match}}.";

// Match only content from single gullwing braces
var matches = new System.Text.RegularExpressions.Regex(@"(?<!{){([^}{]+)}(?!})").Matches(example);

// Go through each match and output it
foreach(System.Text.RegularExpressions.Match match in matches)
{
    // You only want to grab the content within a given group
    Console.WriteLine(match.Groups[1].Value);
}

Answer 2

Would something like this be suitable?

(?<!(^|){){[^}{]*}

It uses a negative lookbehind.

This isn't complete, but it works for your example string. I'm not sure what you expect to happen in a situation where there are characters between the double curly braces.

eg: 'This is {fooo} asdfads {{bar} xxx }' or 'This is {foo} asdf { xx {bar}}'.

Be careful, the other answer posted (which is much better than mine btw) seems to pick up ' xx {bar' as a match to my second example.