Answer by Panagiotis Kanavos for regex c# extracting url from tag

Regular expressions can be used in very specific, simple cases with HTML. For example, if the text contains only a single tag, you can use "href\\s*=\\s*\"(?<url>.*?)\"" to extract the URL, eg:

var url=Regex.Match(text,"href\\s*=\\s*\"(?<url>.*?)\"").Groups["url"].Value;

This pattern will return :

https://website.com/-id1

This regex doesn't do anything fancy. It looks for href= with possible whitespace and then captures anything between the first double quote and the next in a non-greedy manner (.*?). This is captured in the named group url.

Anything more fancy and things get very complex. For example, supporting both single and double quotes would require special handling to avoid starting on a single and ending on a double quote. The string could multiple <a> tags that used both types of quotes.

For complex parsing it would be better to use a library like AngleSharp or HtmlAgilityPack