ManyToMany field can't get the value

Question

User-323784514 posted

Hi,

I have 2 models and they have a Property with ManyToMany relationship, I've put some sample data in my PostgreSql database related tables which created by EntityFramework6, and can correctly see the json format data via a ASP.NET WEB API application, so this test indicates the data are all correct.

Later I want show and support editing for these models in a web page, so I choose the ASP.NET Dynamic Data, the problem is that ManyToMany field always empty in List page, by set a break point to Field template of ManyToMany.ascx, I can see the entityCollection always null via:

var entityCollection = Column.EntityTypeProperty.GetValue(entity, null);

the more detail question is posted at:

http://stackoverflow.com/questions/39952062/cant-retrieve-manytomany-field-value-in-asp-net-dynamic-data

could you help?

Answer 1

User-330204900 posted

Hi Shawn, what project template are you using and what version of Visual Studio are you on?

Answer 2

User-323784514 posted

it's vs2015 community version, the project template is the 'ASP.NET Dynamic Data Entities Web Application'

I believe the template I installed is from https://visualstudiogallery.msdn.microsoft.com/9402d38e-2a85-434e-8d6a-8fc075068a42   which published as a top most post in this forum,  and I just manually un-zipped the MicrosoftAspNetTemplates.vsix  , I can see the template code matches mine.

Answer 3

User-323784514 posted

And one more thing may off the topic, I noticed one line of code obviously missed a null check in ManyToMany_Edit.ascx.cs, and always cause an exception:

        private static bool ListContainsEntity(MetaTable table, IEnumerable<object> list, object entity)
        {
            // the below null check was not existed in original template code, and this is necessary, otherwise, if Model's ManyToMany property
            // is not filled with data, then exception will popup.
            //if (list == null) return false;
            return list.Any(e => AreEntitiesEqual(table, e, entity));
        }

Answer 4

User-330204900 posted

OK then that is all good for this to work, so I will have to say there must be something in your model that is causing this. Can you post the two entities that are in this relationship please.

Answer 5

User-323784514 posted

I've posted all details on that link to stackoverflow.com, i'll copy the definition of models again:

public class PosTransactionModel
{
    public int Id { get; set; }
    public ICollection<PosItemModel> SaleItems { get; set; }
    ...
    ...
}

public class PosItemModel
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]       
    public int ItemId { get; set; }
    public ICollection<PosTransactionModel> SoldInPosTransactions { get; set; }
}

Answer 6

User-330204900 posted

OK I've asked someone who knows EF6 and Code First better then me to have a look.

Answer 7

User-323784514 posted

Any progress on this?

thx!

Answer 8

User-707554951 posted

Hi shawn.shao,
[by debugging, I can see the entityCollection always null, anything I've missed?]
According your description in stackoverflow, I suggest you could to the check whether there is data in rowDescriptor.GetPropertyOwner(null) and Row through debugging your code.
Best regards
Cathy

Answer 9

User-323784514 posted

public partial class ManyToManyField : System.Web.DynamicData.FieldTemplateUserControl
{
        protected override void OnDataBinding(EventArgs e)
        {
            base.OnDataBinding(e);

            object entity;
            //!!!! Row is not null, type is: Microsoft.AspNet.EntityDataSource.EntityDataSourceWrapper
            ICustomTypeDescriptor rowDescriptor = Row as ICustomTypeDescriptor;
            //!!!! rowDescriptor is not null
            if (rowDescriptor != null)
            {
                //!!!! entity is not null, type is: PosTransactionModel
                entity = rowDescriptor.GetPropertyOwner(null);
            }
            else
            {
                entity = Row;
            }

            //!!!! entityCollection is null, and Column = {MetaChildrenColumn SaleItems} and Column.EntityTypeProperty = {System.Collections.Generic.ICollection`1[SharedModel.PosItemModel] SaleItems}
            var entityCollection = Column.EntityTypeProperty.GetValue(entity, null);
            var realEntityCollection = entityCollection as RelatedEnd;
            if (realEntityCollection != null && !realEntityCollection.IsLoaded)
            {
                realEntityCollection.Load();
            }

            Repeater1.DataSource = entityCollection;
            Repeater1.DataBind();
        }

see the code comments to see the debug info.

additional, by set a break point here in first Default page, I always can see the `firstTrx` with all property data correctly loaded:

public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            ApplicationDbContext db = new ApplicationDbContext();
            var firstTrx = db.PosTransactionModels.Include(t => t.SaleItems).ToList().First();
            Console.WriteLine(firstTrx.ToString());

Answer 10

User-323784514 posted

any progress?

thanks!

Answer 11

User-330204900 posted

I have asked someone to have a look but not heard anything back I will ask again :)