如果特定字符串在一行中出现多次，则正则表达式匹配一行

Question

I know how to search for two different specific strings in one line, but not how to check if a single specific string occurs more than once in a line. Can this be done? Whether it matches the whole line or if it matches the strings themselves is not important to me.

Example:

I would like to specify 'Spani' and have it match

The Spaniard speaks Spanish

but not:

The Spaniard speaks German

Can something like this be done with Regex that I am unaware of? If not, is there a way to check the inverse, which is basically the same thing:

Does a specific string only occur once in a line?

Answer 1

Seems like that would be pretty simple:

Spani.+Spani

Assuming you have "Spani" in a variable

var toMatch = "Spani";

var pattern = $"{toMatch}.+{toMatch}";

(Don't include Regex special characters in toMatch .)

Answer 2

You can build a regex similar to that noted in @Steven Doggart's comment above so that you end up with: ^.*(Spani.*){2}$

You should use Regex.Escape to ensure you don't search for any regex reserved characters.

using System.Text.RegularExpressions;

public bool HasMatches(string input, string search, int times)
{
    var pattern = $"^.*({Regex.Escape(search)}.*){{{times}}}";
    return Regex.IsMatch(input, pattern, RegexOptions.Multiline);
}

And run it like this:

var input = "The Spaniard speaks Spanish";
HasMatches(input, "Spani", 2);

input = "The Spaniard speaks German";
HasMatches(input, "Spani", 2);

input = "The Spaniard speaks Spanish" + Environment.NewLine + "The Spaniard speaks German";
HasMatches(input, "Spani", 2);