Search string against "%"

Question

I am trying to write a c# search function that supports "%" in SQL like operator in searching. For eg,

"%m%" will match all strings like below.

some
me
sum
etc..

"%m%e" will match strings something like "some".

Rubens Farias · Accepted Answer · 2011-10-20T10:20:33.467

5

static bool Like(string expression, string value)
{
    return Regex.IsMatch(value, "^" + 
        Regex.Escape(expression).Replace("%", @"[\s\S]*?") + "$", 
        RegexOptions.IgnoreCase);
}

edited Oct 20 '11 at 10:20

answered Oct 20 '11 at 10:15

Rubens Farias

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Good catch using `Regex.Escape` to prevent invalid regex patterns. – Anders Marzi Tornblad Oct 20 '11 at 10:20
+1 I was writing "it's perfect. The first regex written correctly (and perfectly" in one shot (a record) ). But then I noticed you didn't anchor it :-) The string `Hello` will match `Hello World` :-) – xanatos Oct 20 '11 at 10:20
1

@Rubens: you've forgot about LIKE's escape character `!`. :) You need a "real" parser. – Vlad Oct 20 '11 at 10:22
@Ruben, How can I make it case insensitive?? – Kai Oct 20 '11 at 10:22
1

@RubensFarias `var result = Like("Hello", "Hello World"); // Should be false, it's true` – xanatos Oct 20 '11 at 10:23
@Kai, using `RegexOptions` you can control case sensitivity. Updated – Rubens Farias Oct 20 '11 at 10:26

robyaw · Answer 2 · 2011-10-20T10:25:11.217

3

public bool SqlWildcardMatch(string input, string sqlLikePattern)
{
     sqlLikePattern = Regex.Replace(sqlLikePattern, "^([^%])", "^$1");
     sqlLikePattern = Regex.Replace(sqlLikePattern, "([^%])$", "$1$$");

     return Regex.IsMatch(input, string.Replace(sqlLikePattern, "%", ".*"));
}

This function will likely need refining to ensure sqlLikePattern doesn't produce an invalid regex pattern, but consider it a starting point.

edited Oct 20 '11 at 10:25

answered Oct 20 '11 at 10:14

robyaw

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Thanks..I think it is what I'm looking for.Let me try. – Kai Oct 20 '11 at 10:16
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beware with `sqlLikePattern` with regex characters; you must sanitize them first – Rubens Farias Oct 20 '11 at 10:18
And you have to translate `_` as `.`. And you need to support LIKE's escape character `!`. – Vlad Oct 20 '11 at 10:20

score 1 · Answer 3 · edited May 23 '17 at 09:59

1

If you also want to have the way SQL's LIKE treats underscores, you could use my answer to C# Version Of SQL LIKE and if not, you could remove the bit Replace('_', '.').

edited May 23 '17 at 09:59

Community

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answered Oct 20 '11 at 11:25

Jon Hanna

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score 0 · Answer 4 · answered Oct 20 '11 at 10:14

0

You could realize that using regular expressions.

Please have a look at:

http://www.codeproject.com/KB/recipes/wildcardtoregex.aspx

answered Oct 20 '11 at 10:14

dknaack

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score 0 · Answer 5 · answered Oct 20 '11 at 10:14

0

what about using regex .*m.*

answered Oct 20 '11 at 10:14

Mubashir Khan

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Search string against "%"

5 Answers5