Using $expand between customModels

Question

I have:

Visual Studio 2015+Asp.Net web API+MySql Database+Ado.net Datamodel+EF 6+Odata v3

I have 2 customModels getting Data from other "myDBEntities"

../api/myCustomModel1 - works fine

../api/myCustomModel2 - works fine

../api/myCustomModel1?$expand=myCustomModel2 - crash

Error:

The specified type member 'myCustomModel2' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

myCustomModels:

public class myCustomModel1
{
    public byte idL{ get; set; }
    [Key]
    public int idP{ get; set; }
    public string Name { get;set ;  }

    public virtual ICollection<myCustomModel2> myCustomModel2{ get; set; }
}


public class myCustomModel2
{
    public byte idL{ get; set; }
    [ForeignKey("myCustomModel1")]
    public int fk_idP { get; set; }
    public myCustomModel1 myCustomModel1 { get; set; }
    [Key]
    public long idT{ get; set; }
    public string Name { get; set; }       
}

CustomModel1 Controller:

    private static ODataValidationSettings _validationSettings = new ODataValidationSettings();
    private myDBEntities db = new myDBEntities();

    // GET: api/myCustomModel1
    [EnableQuery]
    public IQueryable<myCustomModel1> GetmyCustomModel1()
    {

        var x = (from p in db.table1
                 join l in db.table2 on p.column equals l.column 
                 select new myCustomModel1{ idL= p.idL, idP= p.idP, Name = String.Concat(l.Name, p.Name) });

        return x;
    }

CustomModel2 Controller:

    private static ODataValidationSettings _validationSettings = new ODataValidationSettings();


    private myDBEntities db = new myDBEntities ();

    // GET: api/myCustomModel2
    [EnableQuery]
    public IQueryable<myCustomModel2> GetmyCustomModel2()
    {

        var x = (from t in db.table3
                 join l in db.table2 on t.column equals l.column
                 select new myCustomModel2{ idL= t.idL, fk_idP= t.idP,idT= t.idT, Name = String.Concat(l.Name, t.Name) });
        return x;
    }

My Question is: What needs to be done to use

"../api/myCustomModel1?$expand=myCustomModel2" ?

Answer 1

I solved this problem this way:

My Custom Models:

public class myCustomModel1
{
   public byte idL { get; set; }
   [Key]
   public int idP { get; set; }
   public string Name { get; set; }
   public virtual List<myCustomModel2> CustomModel2{ get; set; }
}

public class myCustomModel2
{
   public int idData { get; set; }
}

My controller:

public class myCustomModel1Controller: ODataController
{
    private static ODataValidationSettings _validationSettings = new ODataValidationSettings();       
    private IRepository _repo = new Repository();

    [EnableQuery]
    public IEnumerable<myCustomModel1> GetmyCustomModel1([FromODataUri] int key)
    {          
        return _repo.FetchDataForcustomModel1(key);
    }
}

my Interface & Repository:

public interface IRepository
{
   IEnumerable<myCustomModel1> FetchDataForcustomModel1(int key);
}
public class Repository : IRepository
{
   private my_dbEntities db = new my_dbEntities(); //Created with Entity Framework - needed to fill my model with database data

   public IEnumerable<myCustomModel1> FetchDataForcustomModel1(int key);
   {                   
        IEnumerable<myCustomModel1> myModelData= (from d in db.table1                           
                              where d.idD == key                                 
                              select new myCustomModel1
                              {
                                 idL = d.idL,
                                 idP = d.idP,
                                 Name = d.Name
                                 CustomModel2= (from l in db.table2
                                          where l.fkidD == d.idD                                           
                                          select new myCustomModel2
                                          {
                                              idData = l.fkidD                                             
                                          }).ToList()
                              }).ToList();
        return myModelData;

  }
}

Added EntitySet to WebApiConfig.cs

    builder.EntitySet<myCustomModel1>("myCustomModel1");
    builder.EntitySet<myCustomModel2>("myCustomModel2");

Now i can use: /api/myCustomModel1?$expand=CustomModel2

If you want to have "CustomModel2" autoexpanded remove the EntitySet for "myCustomModel2" in WebApiConfig.cs

I hope this answer is helpful