Unable to persist an IList using <list> mapping, bug?

neil_janabi · **Joined:** Wed Aug 16, 2006 12:56 pm **Posts:** 4

Hi,

I am having problems peristing an IList using the <list> mapping.

I am pretty sure my mappings are correct as I have already got an IDictionary persisting using <map>, so I have experience how collection mappings are defined.

I have used the debugger to step through the Nhibernate-1.0.2.0 code and the problem seems to be in

Code:

NHibernate.Impl.OnUpdateVisitor

in the method

Code:

protected override object ProcessCollection(object collection, PersistentCollectionType type)

line 42

Code:

if( collection is PersistentCollection )

Seems my IList collection should be getting replaced with the equivalent PersistentCollection type.

Originally I defined my collection as a

Code:

System.Collections.Generic.List<T>

, which I thought was the problem,
but then I tried redefining it as a

Code:

System.Collections.Arraylist

, which didn't work either.

I think it is a bug, does anyone know of a work around?

Thanks, Neil

gert · **Joined:** Thu Jan 19, 2006 4:29 pm **Posts:** 348

neil_janabi wrote:

Seems my IList collection should be getting replaced with the equivalent PersistentCollection type.

Originally I defined my collection as a

Code:

System.Collections.Generic.List<T>

, which I thought was the problem,

Your class proeprty and field must be of type IList<t>, not List<T>

Code:

private System.Collections.Generic.IList<T> m_MyCollection;

public System.Collections.Generic.IList<T> MyCollection
{
  get {return m_MyCollection; }
}

Gert

neil_janabi · **Joined:** Wed Aug 16, 2006 12:56 pm **Posts:** 4

I am still using version 1.0.2.0 which I didn't think supported generics.

Anyway I tried persisting my list as

Code:

private List<UserPortfolioExchangeProduct> _userPortfolioExchangeProducts;

private IList PersistedUserPortfolioExchangeProducts
{
    get
    {
        IList list = new ArrayList(_userPortfolioExchangeProducts);
        return list;
    }
}

Which also returns false in

Code:

NHibernate.Impl.OnUpdateVisitor

method

Code:

protected override object ProcessCollection(object collection, PersistentCollectionType type) 

line 42

Code:

if( collection is PersistentCollection )

gert · **Joined:** Thu Jan 19, 2006 4:29 pm **Posts:** 348

neil_janabi wrote:

I am still using version 1.0.2.0 which I didn't think supported generics.

In this case, both property and field in class must be of IList type. I.e.

Code:

private System.Collections.IList m_MyCollection = new ArrayList();

public System.Collections.IList MyCollection
{
  get {return m_MyCollection; }
}

neil_janabi · **Joined:** Wed Aug 16, 2006 12:56 pm **Posts:** 4

Sorry I ommited the setter in my last sample snippet, as in my code

Code:

        private IList PersistedUserPortfolioExchangeProducts
        {
            get
            {
                IList list = new ArrayList(_userPortfolioExchangeProducts);
                return list;
            }
            set
            {
                // TODO
            }
        }

So the problem still exists

I did a similar thing with a generic dictionary cast to an IDictionary mapped to a <map> which worked OK, snippet

Code:

private Dictionary<PricingUnit, PricingUnitsConversion> _pricingUnitsConversions; 

    private IDictionary PricingUnitsConversions
    {
        get
        {
            return _pricingUnitsConversions;
        }
        set
        {
           _pricingUnitsConversions =
                new Dictionary<PricingUnit, PricingUnitsConversion>(value.Count);

            foreach (PricingUnit pricingUnit in value.Keys)
                _pricingUnitsConversions[pricingUnit] =
                    (PricingUnitsConversion)value[pricingUnit];
        }
    }

Still think the problem is in the Nhibernate code as both List<T> and ArrayList implement System.Collections.IList

gert · **Joined:** Thu Jan 19, 2006 4:29 pm **Posts:** 348

neil_janabi wrote:

Sorry I ommited the setter in my last sample snippet, as in my code

Code:

        private IList PersistedUserPortfolioExchangeProducts
        {
            get
            {
                IList list = new ArrayList(_userPortfolioExchangeProducts);
                return list;
            }
            set
            {
                // TODO
            }
        }

So the problem still exists

I did a similar thing with a generic dictionary cast to an IDictionary mapped to a <map> which worked OK, snippet

Code:

private Dictionary<PricingUnit, PricingUnitsConversion> _pricingUnitsConversions; 

    private IDictionary PricingUnitsConversions
    {
        get
        {
            return _pricingUnitsConversions;
        }
        set
        {
           _pricingUnitsConversions =
                new Dictionary<PricingUnit, PricingUnitsConversion>(value.Count);

            foreach (PricingUnit pricingUnit in value.Keys)
                _pricingUnitsConversions[pricingUnit] =
                    (PricingUnitsConversion)value[pricingUnit];
        }
    }

Still think the problem is in the Nhibernate code as both List<T> and ArrayList implement System.Collections.IList

First of all, this setter is not very perfomance-wise, as NHibernate is not able to track the changes made to collection. Second, it is not adviceable to have setters for collection proeprties (as per MS guidelines)

But going back to Your problem with IList: what is the access strategy for collection? If it involves fields (Like nosetter-smth), try changing. Otherwise, post actual code and mapping (whole map file) for the problematic class.

Gert