SqlLinq: Taking LINQ to SQL in the Other Direction

using System;
using System.Linq;
using System.Reflection;
using System.Linq.Expressions;
using System.Text.RegularExpressions;

namespace SqlLinq.SyntaxTree.Predicates.Comparison
{
    [SyntaxNode(RuleConstants.RULE_PREDEXP_LIKE_STRINGLITERAL)]
    public class LikeNode : PredicateNode
    {
        public LikeNode()
            : base(typeof(string), typeof(bool))
        {
        }

        protected override Expression CreateOperatorExpression(ParameterExpression param, Expression left)
        {
            MethodInfo match = typeof(LikeNode).GetMethod("IsSqlLikeMatch");
            Expression pattern = Expression.Constant(GetTerminalText("StringLiteral").Trim('\''));
            return Expression.Call(match, left, pattern);
        }

        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);
        }
    }
}