LINQ search using WildCards character like *, %,?

Question

Hi I have a collection of name type objects and I want to perform a wild card search on it. For example, if I provide a search Criteria *ABC then the returned name should start with ABC. If I provide a search Criteria ABC* then returned name should end with ABC. If I provide a search Criteria *ABC* then returned name should contains ABC. If I provide a search Criteria ?ABC then returned name's second, third and fourth character should be ABC respectively and first character can be any character.

Answer 1

Here's an extension method you might use

public static class EnumerableExtensions
{
    public static IEnumerable<T> MatchesWildcard<T>(this IEnumerable<T> sequence, Func<T,string> expression, string pattern)
    {
        var regEx = WildcardToRegex(pattern);

        return sequence.Where(item => Regex.IsMatch(expression(item), regEx));
    }

    public static string WildcardToRegex(string pattern)
    {
        return "^" + Regex.Escape(pattern).
        Replace("\\*", ".*").
        Replace("\\?", ".") + "$";
    }
}

Use it as follows:

void Main()
{
    var items = new[] { new MyObj { MyProperty = "ABC123" },
                        new MyObj { MyProperty = "123ABC" },
                        new MyObj { MyProperty = "123ABC456" },
    };

    var matches = items.MatchesWildcard(item => item.MyProperty, "???ABC");
}

public class MyObj
{
    public string MyProperty {get;set;}
}

(WildcardToRegex taken from CodeProject)

Answer 2

I think you need Regex.Escape and Regex.IsMatch().

private IEnumerable<Item> FilterList(IEnumerable<Item> list, string query)
{
    string pattern = QueryToRegex(query);

    return list.Where(i => Regex.IsMatch(i.Name, pattern, RegexOptions.Singleline));
}

private static string QueryToRegex(string query)
{
    return "^" + Regex.Escape(query).Replace("\\*", ".*").Replace("\\?", ".") + "$";
}

Note: Samuel Jack's answer was better in that his Regex was better, so shamefully fixed it here.