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".
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5 Answers
5
static bool Like(string expression, string value)
{
return Regex.IsMatch(value, "^" +
Regex.Escape(expression).Replace("%", @"[\s\S]*?") + "$",
RegexOptions.IgnoreCase);
}
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
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+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
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1@Rubens: you've forgot about LIKE's escape character `!`. :) You need a "real" parser. – Vlad Oct 20 '11 at 10:22
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@Ruben, How can I make it case insensitive?? – Kai Oct 20 '11 at 10:22
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1@RubensFarias `var result = Like("Hello", "Hello World"); // Should be false, it's true` – xanatos Oct 20 '11 at 10:23
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@Kai, using `RegexOptions` you can control case sensitivity. Updated – Rubens Farias Oct 20 '11 at 10:26
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.
robyaw
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2beware with `sqlLikePattern` with regex characters; you must sanitize them first – Rubens Farias Oct 20 '11 at 10:18
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And you have to translate `_` as `.`. And you need to support LIKE's escape character `!`. – Vlad Oct 20 '11 at 10:20
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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('_', '.').
0
You could realize that using regular expressions.
Please have a look at:
dknaack
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