Question

On ASP.NET MVC 3, I created a Action Filter for white space removal from the entire html. It works as I expected most of the time but now I need to change the RegEx in order not to touch inside pre element.

I get the RegEx logic from awesome Mads Kristensen‘s blog and I am not sure how to modify it for this purpose.

Here is the logic:

public override void Write(byte[] buffer, int offset, int count) {

    string HTML = Encoding.UTF8.GetString(buffer, offset, count);

    Regex reg = new Regex(@"(?<=[^])\t{2,}|(?<=[>])\s{2,}(?=[<])|(?<=[>])\s{2,11}(?=[<])|(?=[\n])\s{2,}");
    HTML = reg.Replace(HTML, string.Empty);

    buffer = System.Text.Encoding.UTF8.GetBytes(HTML);
    this.Base.Write(buffer, 0, buffer.Length);
}

Whole code of the filter:

https://github.com/tugberkugurlu/MvcBloggy/blob/master/src/MvcBloggy.Web/Application/ActionFilters/RemoveWhitespacesAttribute.cs

Any idea?

EDIT:

BIG NOTE:

My intention is totally not speed up the response time. In fact,
maybe this slows things down. I GZiped the pages and this minification makes me
gain approx 4 – 5 kb per page which is nothing.

Answer 1

Parsing HTML with regex very complicated and any simple solutions could break easily. (Use the right tool for the job.) That being said I’ll show a simple solution.

First I simplified the regex you had to:

(?<=\s)\s+

Replace those matches with an empty string to get rid of double spaces everywhere.

Assuming there are no < or > inside the pre tag, you can add (?![^<>]*</pre>) at the end of the expression to make it fail inside of pre tags. This makes sure that </pre> doesn’t follow current match, without any tags in between.

Resulting in:

(?<=\s)\s+(?![^<>]*</pre>)