這段代碼將模仿Sql LIKE的行爲和語法。你可以把它包裝成自己的拉姆達或擴展方法LINQ的聲明中使用:
public static bool IsSqlLikeMatch(string input, string pattern)
{
/* Turn "off" all regular expression related syntax in
* the pattern string. */
pattern = Regex.Escape(pattern);
/* Replace the SQL LIKE wildcard metacharacters with the
* equivalent regular expression metacharacters. */
pattern = pattern.Replace("%", ".*?").Replace("_", ".");
/* The previous call to Regex.Escape actually turned off
* too many metacharacters, i.e. those which are recognized by
* both the regular expression engine and the SQL LIKE
* statement ([...] and [^...]). Those metacharacters have
* to be manually unescaped here. */
pattern = pattern.Replace(@"\[", "[").Replace(@"\]", "]").Replace(@"\^", "^");
return Regex.IsMatch(input, pattern, RegexOptions.IgnoreCase);
}
粗化一起擴展方法,將工作就像IEnumerable<T>.Where
方法:
public static IEnumerable<T> Like<T>(this IEnumerable<T> source, Func<T, string> selector, string pattern)
{
return source.Where(t => IsSqlLikeMatch(selector(t), pattern));
}
將要在轉允許您格式化的語句,像這樣:
string pattern = "%ine%e";
var res = list.Like(s => s, pattern);
編輯 的即興如果有人偶然想要使用這個代碼,它轉換和編譯正則表達式一次,而不是每個項目,從上面的LIKE到正則表達式的轉換有一些錯誤。
public static class LikeExtension
{
public static IEnumerable<T> Like<T>(this IEnumerable<T> source, Func<T, string> selector, string pattern)
{
var regex = new Regex(ConvertLikeToRegex(pattern), RegexOptions.IgnoreCase);
return source.Where(t => IsRegexMatch(selector(t), regex));
}
static bool IsRegexMatch(string input, Regex regex)
{
if (input == null)
return false;
return regex.IsMatch(input);
}
static string ConvertLikeToRegex(string pattern)
{
StringBuilder builder = new StringBuilder();
// Turn "off" all regular expression related syntax in the pattern string
// and add regex begining of and end of line tokens so '%abc' and 'abc%' work as expected
builder.Append("^").Append(Regex.Escape(pattern)).Append("$");
/* Replace the SQL LIKE wildcard metacharacters with the
* equivalent regular expression metacharacters. */
builder.Replace("%", ".*").Replace("_", ".");
/* The previous call to Regex.Escape actually turned off
* too many metacharacters, i.e. those which are recognized by
* both the regular expression engine and the SQL LIKE
* statement ([...] and [^...]). Those metacharacters have
* to be manually unescaped here. */
builder.Replace(@"\[", "[").Replace(@"\]", "]").Replace(@"\^", "^");
// put SQL LIKE wildcard literals back
builder.Replace("[.*]", "[%]").Replace("[.]", "[_]");
return builder.ToString();
}
}
哇!它最令人敬畏的答案比別人!非常感謝你 – 2011-04-14 13:20:07