Question with PredicateBuilder multiple AND OR

I've a question about the PredicateBuilder and I really hope you can give me some advice on how to solve this. I'll try to explain this.

I have the case where people can search for products based on keywords. Each keyword belongs to a keywordgroup, so some real data would be:

KeywordGroup / Keyword

Type - Chain/

Type - Bracelet/

Color - Purple/

Color - Green

Now I want to have the following results:

Between each different KeywordGroup there should be an OR. Between each different Keyword inside a KeywordGroup there should be an AND.

So e.g., a user want's to search for only Bracelets with the colors Purlple or Green.

Is this possible with this PredicateBuilder?

This is what I have so far:

================================

/// <summary>
    /// Search for products
    /// </summary>
    /// <param name="itemsPerPage"></param>
    /// <returns></returns>
    public List<Product> SearchProducts(int from, int max, string sorting, List<Keyword> filter, out int totalitems) {
        try {

            var predicate = PredicateBuilder.True<Product>();
            KeywordGroup previousKeywordGroup = null;
            foreach (Keyword k in filter.OrderBy(g=>g.KeywordGroup.SortOrder)) {
                if (previousKeywordGroup != k.KeywordGroup) {
                    previousKeywordGroup = k.KeywordGroup;

                    predicate = predicate.And(p => p.Keywords.Contains(k));
                }
                else
                    predicate = predicate.Or(p => p.Keywords.Contains(k));
            }

            var products = context.Products.AsExpandable().Where(predicate);
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            //var products = from p in context.Products
            //               from k in p.Keywords
            //               where filter.Contains(k)
            //               select p;

            totalitems = products.Distinct().Count();
            if (sorting == "asc")
                return products.Where(x => x.Visible == true).Distinct().Skip(from).Take(max).OrderBy(o => o.SellingPrice).ToList();
            else
                return products.Where(x => x.Visible == true).Distinct().Skip(from).Take(max).OrderByDescending(o => o.SellingPrice).ToList();
        }
        catch (Exception ex) {
            throw ex;
        }
    }

================================

It doesn't work, though.

Can you help me out?

Thanks! Daniel

You need to use a temporary variable in the loop for each keyword. From the Predicate Builder page:

The temporary variable in the loop is required to avoid the outer variable trap, where the same variable is captured for each iteration of the foreach loop.

Try this instead:

foreach (Keyword k in filter.OrderBy(g=>g.KeywordGroup.SortOrder)) {
    Keyword temp = k;
    if (previousKeywordGroup != k.KeywordGroup) {
        previousKeywordGroup = k.KeywordGroup;

        predicate = predicate.And(p => p.Keywords.Contains(temp));
    }
    else
        predicate = predicate.Or(p => p.Keywords.Contains(temp));
}

Notice the use of temp in each line where predicate And and Or are used.

This is just making a big list of And ands Or statements, you need to group them together.

Something like this..

        var grouped = filter.GroupBy(item => item.KeyWordGroup, item => item.KeyWords);

        foreach (var item in grouped)
        {
            var innerPredicate = PredicateBuilder.True<Product>();
            foreach (var inner in item)
            {
                innerPredicate = innerPredicate.Or(p => item.Contains(k));  
            }
            predicate = predicate.And(innerPredicate);  //not sure this is correct as dont have IDE..
        }