Regular Expression help in C# - .+ OR [^$]+$

Question

On a single line Regex if I want to capture all till the end of line.. Which of these will be better in terms of Performance?

Regex r = new Regex(".+");

OR

Regex r = new Regex("[^$]+$");

I haven't included the entire regex but I hope you get the idea.

Are there any trade-offs or they both behave the same way?

Thanks!

Answer 1

Using a StringReader seems more appropriate:

using (var reader = new StringReader(someString))
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        // You capture the line here
    }
}

Answer 2

I suspect that you misunderstand what the second regex, [^$]+, actually does. It matches one or more characters other than the literal $. So it will match the entire string, including line breaks. So it does something different than .+ matches. Therefore, they can't just be compared to each other.

Answer 3

What you're doing is called premature optimization. Performance is nice to have, but you should also keep your code simple and readable.
.+$ means "read everything until the end" - it is obvious, why complicate it? Later, if your program is slow, you profile it and try to figure out why (common bottlenecks are data queries and network - but don't assume anything).
This is a good example of why not to optimize too soon; having good intentions you've complicated your code and introduced errors: [^$]+$ does not have the meaning you though it had.