Use MultiValueDictionary instead of Dictionary with NHibernate.Criterion.Restrictions

Question

Currently, I have this code, which works, getting a foodList:

var myDictionary = new System.Collections.Generic.Dictionary<string, object>();
myDictionary .Add("RefId",1);
myDictionary.Add("Type", "fruit");
var foodList = this.factoryService.GetMyService()
                    .GetByCriteria(sortOrder, NHibernate.Criterion.Restrictions.AllEq(myDictionary));

I want to use MultiValueDictionary so as to gather more than one Type.

var multiValueDictionary = new System.Collections.Generic.MultiValueDictionary<string, object>();
multiValueDictionary.Add("RefId",1);
multiValueDictionary.Add("Type", "fruit");
multiValueDictionary.Add("Type", "vegetable");
multiValueDictionary.Add("Type", "fungus");

var foodList = this.factoryService.GetMyService()
                    .GetByCriteria(sortOrder, NHibernate.Criterion.Restrictions.AllEq(multiValueDictionary));

That last line doesn't compile because MultiValueDictionary does not implement IDictionary, giving the error:

Error CS1503 Argument 1: cannot convert from 'System.Collections.Generic.MultiValueDictionary' to 'System.Collections.IDictionary'

How can I do this?

Answer 1

AllEq implementation is simply:

/// <summary>
/// Apply an "equals" constraint to each property in the key set of a IDictionary
/// </summary>
/// <param name="propertyNameValues">a dictionary from property names to values</param>
/// <returns></returns>
public static AbstractCriterion AllEq(IDictionary propertyNameValues)
{
    Conjunction conj = Conjunction();

    foreach (DictionaryEntry item in propertyNameValues)
    {
        conj.Add(Eq(item.Key.ToString(), item.Value));
    }

    return conj;
}

So for your multi-value case, you could cease putting it in the dictionary and manually add it afterward:

var myDictionary = new Dictionary<string, object>();
myDictionary.Add("RefId", 1);

var filter = (Conjunction)Restrictions.AllEq(myDictionary);
filter.Add(Restrictions.In("Type", new [] {"fruit", "vegetable", "fungus"});

var foodList = this.factoryService.GetMyService()
    .GetByCriteria(sortOrder, filter);

Of course if you now only have RefId to put in your dictionary, better simplify it:

var filter = Restrictions.Conjunction();
filter.Add(Restrictions.Eq("RefId", 1));
filter.Add(Restrictions.In("Type", new [] {"fruit", "vegetable", "fungus"}));

var foodList = this.factoryService.GetMyService()
    .GetByCriteria(sortOrder, filter);

Now if you want an AllIn handling multi-values, code it:

public static AbstractCriterion AllIn<TValue>(
    MultiValueDictionary<string, TValue> propertyNameValues)
{
    var conj = Restrictions.Conjunction();

    foreach (KeyValuePair<TKey, IReadOnlyCollection<TValue>> item in propertyNameValues)
    {
        if (item.Value.Count > 1)
        {
            conj.Add(Restrictions.In(item.Key, item.Value.ToArray()));
        }
        else
        {
            conj.Add(Restrictions.Eq(item.Key, item.Value.FirstOrDefault()));
        }
    }

    return conj;
}