Regex Match Alphanumeric values with specific conditions

Question

I need to match a string under the following conditions using Regex in C#:

Entire string can only be alphanumeric (including spaces). Example string should only match are: ( numerical values can change)

Example1 String: best 5 products

Example2 String: 5 best products

Example3 String: products 5 best

I am looking to get get "5 best" or "best 5" but the following strings are also matching:

Example1 String: best anything 5 products

Example2 String: 5 anything best products

Example3 String: products 5 anything best

I am using:

string utter11 = Console.ReadLine();

string pattern11 = "^(?=.*best)(?=.*[0-9]).*$";

bool match = Regex.IsMatch(utter11, pattern11, RegexOptions.IgnoreCase);
Console.WriteLine(match);

Any suggestions are welcome. Thanks

Try this Regular expression : (best\s\d*)|(\d*\sbest)|(\d)

Anurag Jain
– Anurag Jain

2014-01-17 16:08:29 +00:00
Commented Jan 17, 2014 at 16:08 — Anurag Jain
– Anurag Jain, Commented Jan 17, 2014 at 16:08

Jerry · Accepted Answer · 2014-01-17 15:55:18Z

1

You might try this which I made as close as possible to your regex:

^(?=.*(?:best [0-9]|[0-9] best)).*$

regex101 demo

If you want to get capture groups, just make a minor change:

^(?=.*(best [0-9]|[0-9] best)).*$

regex101 demo

It's basically looking for best [0-9] or [0-9] best, which I understood is what you're looking for.

answered Jan 17, 2014 at 15:55

Jerry

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4 Comments

dee-see Over a year ago

From OP: "Entire string can only be alphanumeric (including spaces)". I think you should change the . to a character class.

Jerry Over a year ago

@Vache I wonder though why OP is using .* themself. Plus, the strings that are not supposed to match don't seem to have to do anything about being alphanumeric including spaces, but really about the placement of best and the number. Otherwise, I guess we just have to wait for OP to clarify...

Anurag Jain Over a year ago

@Jerry : His trying to get best or 5 in the string pattern but your regex capture whole string. If i am wrong let me know ???

Jerry Over a year ago

@AnuragJain My regex doesn't capture the whole string. It matches the whole string. The second regex I suggested captures only best 5 and 5 best...

Patrick Quirk · Accepted Answer · 2014-01-17 15:53:14Z

0

Try (?:(?<=best)\s+([0-9]))|(?:([0-9])\s+(?=best))

Expects either a prefix of "best" and then whitespace and a number, or a number and whitespace and then a suffix of "best"

answered Jan 17, 2014 at 15:53

Patrick Quirk

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Comments

mrzli · Accepted Answer · 2014-01-17 16:09:32Z

How about this (complete example):

class Program
{
    static void Main(string[] args)
    {
        List<string> validStrings = new List<string>
        {
            "best 5 products",
            "5 best products",
            "products 5 best",
            "best anything 5 products",
            "5 anything best products",
            "products 5 anything best",
        };

        List<string> invalidStrings = new List<string>
        {
            "best 5 products.",
            "5 best product;s",
            "produc.ts 5 best",
            "best anything 5 product/s",
            "5 anything best produc-ts",
            "products 5 anything be_st",
        };

        string pattern1 = @"^(([A-Za-z0-9\s]+\s+)|\s*)[0-9]\s+([A-Za-z0-9\s]+\s+)?best((\s+[A-Za-z0-9\s]+)|\s*)$";
        string pattern2 = @"^(([A-Za-z0-9\s]+\s+)|\s*)best\s+([A-Za-z0-9\s]+\s+)?[0-9]((\s+[A-Za-z0-9\s]+)|\s*)$";
        string pattern = string.Format("{0}|{1}", pattern1, pattern2);

        foreach (var str in validStrings)
        {
            bool match = Regex.IsMatch(str, pattern);
            Console.WriteLine(match);
        }

        Console.WriteLine();

        foreach (var str in invalidStrings)
        {
            bool match = Regex.IsMatch(str, pattern);
            Console.WriteLine(match);
        }

        Console.Read();
    }
}

If you have more examples of what string the pattern should and shouldn't match, I'll refine the expression if necessary.

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