Could not determine the reverse association...

Hello

I am evaluating Lightspeed at the moment becuase we are planning on using it in our current project. I ran right into the first problem and cannont figure out, what the solution might be.

I set up 2 entity classes (Product and CommodityGroup). A Product always belongs to a commodity group so there's the association.

 In my console test app, when I execute the following code...

LightSpeedContext<MoritzUnitOfWork> context = new LightSpeedContext<MoritzUnitOfWork>
{
    PluralizeTableNames = true,
    DataProvider = DataProvider.MySql5,
    IdentityMethod = IdentityMethod.IdentityColumn,
    ConnectionString = @"Server=localhost;Database=moritz_db;Uid=root;Pwd=password;"
};

using (var unitOfWork = context.CreateUnitOfWork())
{
    var filteredProducts = unitOfWork.Products.Where(p => p.Price < 30);
    foreach (Product p in filteredProducts)
    {
        Console.WriteLine(p.Title);
    }
}

... I get a target invocation exception, holding an inner exception with the message:
"Could not determine the reverse association of [Product.CommodityGroup (CommodityGroup)]"

My test entities are really simple:

public class Product : Entity<int>
    {
        #region PRIVATE FIELDS
        [ValidatePresence]
        private string title;
        [ValidatePresence]
        private double price;
       
        private int commodityGroupId;

        private EntityHolder<CommodityGroup> commodityGroup = new EntityHolder<CommodityGroup>();
        #endregion

        #region PUBLIC PROPERTIES
        public string Title
        {
            get { return this.title; }
            set { Set(ref this.title, value); }
        }

        public double Price
        {
            get { return this.price; }
            set { Set(ref this.price, value); }
        }

        public CommodityGroup CommodityGroup
        {
            get { return Get(this.commodityGroup); }
            set { Set(this.commodityGroup, value); }
        }

        public int CommodityGroupId
        {
            get { return this.commodityGroupId; }
            set { Set(ref this.commodityGroupId, value); }
        }
        #endregion
    }

public class CommodityGroup : Entity<int>
    {
        #region PRIVATE FIELDS
        [ValidatePresence]
        private string title;
        #endregion

        #region PUBLIC PROPERTIES
        public string Title
        {
            get { return this.title; }
            set { Set(ref title, value); }
        }
        #endregion
    }

What did I do wrong?

Thanks in advance and greeting from Europe!

André Buss

Hi André,

LightSpeed objects always have bi-directional relationships. Because of this you need to add an EntityCollection<Product> _products field to your CommodityGroup class. LightSpeed will be looking for the reverse association of the EntityHolder<CommodityGroup> to set up.

Try that out and see if that helps :-)

Also - if you use the Visual Studio designer this should all be handled for you. If you have only the express version of VS then try our lsgen.exe that we ship as it will do a first run through and generate the classes for you.

Let me know if that helps and hi from New Zealand :-)

John-Daniel Trask
Mindscape

 Hi John-Daniel

Thank you for the quick resonse. I didn't know that the relationships have to be implemented bi-directionally. It's working now.

I have the VS Team System 2008 and somehow cannot find the Designer within the toolbox. I like coding better than dragging and dropping anyway ;-), so that's no problem.

André

PS.: Is a full featured Linq to MySql support planned for the next version of LightSpeed?