Question

I have a cluttery piece of code that I would like to shorten using Linq. It’s about the part in the foreach() loop that performs an additional grouping on the result set and builds a nested Dictionary.

Is this possible using a shorter Linq syntax?

        var q = from entity in this.Context.Entities
                join text in this.Context.Texts on new { ObjectType = 1, ObjectId = entity.EntityId} equals new { ObjectType = text.ObjectType, ObjectId = text.ObjectId}
        into texts
                select new {entity, texts};

        foreach (var result in q)
        {
            //Can this grouping be performed in the LINQ query above?
            var grouped = from tx in result.texts
                    group tx by tx.Language
                    into langGroup
                    select new
                               {
                                   langGroup.Key,
                                   langGroup
                               };
            //End grouping

            var byLanguage = grouped.ToDictionary(x => x.Key, x => x.langGroup.ToDictionary(y => y.PropertyName, y => y.Text));

            result.f.Apply(x => x.Texts = byLanguage);
        }

        return q.Select(x => x.entity);

Sideinfo:

What basically happens is that “texts” for every language and for every property for a certain objecttype (in this case hardcoded 1) are selected and grouped by language. A dictionary of dictionaries is created for every language and then for every property.

Entities have a property called Texts (the dictionary of dictionaries). Apply is a custom extension method which looks like this:

    public static T Apply<T>(this T subject, Action<T> action)
    {
        action(subject);
        return subject;
    }

Answer 1

isn’t this far simpler?

foreach(var entity in Context.Entities)
{
   // Create the result dictionary.
   entity.Texts = new Dictionary<Language,Dictionary<PropertyName,Text>>();

   // loop through each text we want to classify
   foreach(var text in Context.Texts.Where(t => t.ObjectType == 1 
                                             && t.ObjectId == entity.ObjectId))
   {
       var language = text.Language;
       var property = text.PropertyName;

       // Create the sub-level dictionary, if required
       if (!entity.Texts.ContainsKey(language))
           entity.Texts[language] = new Dictionary<PropertyName,Text>();

       entity.Texts[language][property] = text;
   }
}

Sometimes good old foreach loops do the job much better.

Language, PropertyName and Text have no type in your code, so I named my types after the names…