正则表达式问题 C#

Question

 const string strRegex = @"(?<city_country>.+) ?(bis|zu)? (?<price>[\d.,]+) eur";
            searchQuery = RemoveSpacesFromString(searchQuery);
            Regex regex = new Regex(strRegex, RegexOptions.IgnoreCase);

            Match m = regex.Match(searchQuery);
            ComplexAdvertismentsQuery query = new ComplexAdvertismentsQuery();

            if (m.Success)
            {
                query.CountryName = m.Groups["city_country"].Value;
                query.CityOrAreaName = m.Groups["city_country"].Value;
                query.PriceFrom = Convert.ToDecimal(1);
                query.PriceTo = Convert.ToDecimal(m.Groups["price"].Value);
            }
            else
                return null;

            return query;

my search string is "Agadir ca. 600 eur" but "ca." is not "bis" or "zu" and regex is also true. What is wrong with regex? I want that regex is true only if is word "bis" or "zu".

I think this is worng

?(bis|zu)?

Answer 1

Agadir ca. becomes your city_country and (bis|zu)? part is skipped as you've marked it as not required with ? .

Answer 2

It looks like it's because you made bis and zu optional. Try changing (bis|zu)? to (bis|zu)

Answer 3

Remove the question mark in (bis|zu)? . As it is right now, the .+ of <city_country> matches up to the prices and includes ca. .

In fact, you might want to change the whole ?(bis|zu)? part to ( bis| zu) .

Answer 4

(?<city_country>.+) ?(bis|zu)? (?<price>[\d.,]+) eur
                    ^        ^
                    1        2

1. The first ? belongs to the space before

2. The second ? belongs to the (bis|zu)

The ? in these two cases makes the expression before optional