Entity Framework 4 - Many-To-Many Relationship with a view

Question

I have an entity Group which has a many to many relationship with a view VesselInfo. In database, the relationship is stored in a table, GroupVessel.

public class Group
{
    public Group()
    {
        GroupVessels = new List<GroupVessel>();
    }

    public int GroupId { get; set; }

    public virtual ICollection<GroupVessel> GroupVessels { get; set; }
}

public class GroupVessel
{
    public int GroupVesselId { get; set; }

    public int GroupId { get; set; }
    public virtual Group Group { get; set; }

    public int VesselId { get; set; }
    public virtual VesselView Vessel { get; set; }
}

public class VesselView
{
    public int VesselId { get; set; }
}

The entities are mapped in the context like this:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Configurations.Add(new VesselViewMapping());
    modelBuilder.Configurations.Add(new GroupMapping());
    modelBuilder.Configurations.Add(new GroupVesselMapping());
    base.OnModelCreating(modelBuilder);
}

public class VesselViewMapping : EntityTypeConfiguration<VesselView>
{
    public VesselViewMapping()
    {
        // Primary Key
        HasKey(t => t.VesselId);

        // Properties
        Property(t => t.VesselId)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

        // Table & Column Mappings
        ToTable("v_VesselInfo");
        Property(t => t.VesselId).HasColumnName("VesselId");
    }
}

public class GroupMapping : EntityTypeConfiguration<Group>
{
    public GroupMapping()
    {
        // Primary Key
        HasKey(group => group.GroupId);

        // Properties

        // Table & Column Mappings
        ToTable("Group");
        Property(t => t.GroupId)
            .HasColumnName("GroupId")
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
    }
}

public class GroupVesselMapping : EntityTypeConfiguration<GroupVessel>
{
    public GroupVesselMapping()
    {
        // Primary Key
        HasKey(group => group.GroupVesselId);

        // Properties

        // Table & Column Mappings
        ToTable("GroupVessel");
        Property(t => t.GroupVesselId)
            .HasColumnName("GroupVesselId")
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

        Property(t => t.VesselId).HasColumnName("VesselId").IsRequired();

        Property(t => t.GroupId).HasColumnName("GroupId");

        // Relationships
        HasRequired(t => t.Group).WithMany(g => g.GroupVessels)
                                 .HasForeignKey(t => t.GroupVesselId);
    }
}

When I try to instantiate the context, I get the following error:

Exception Details: System.Data.Entity.ModelConfiguration.ModelValidationException: One or more validation errors were detected during model generation:

\tSystem.Data.Entity.Edm.EdmAssociationEnd: : Multiplicity is not valid in Role 'GroupVessel_Group_Source' in relationship 'GroupVessel_Group'. Because the Dependent Role refers to the key properties, the upper bound of the multiplicity of the Dependent Role must be '1'.

Some additional info: In database, the GroupVessel.VesselId column is a foreign key to a table Vessels, which is the underlying table of the v_VesselInfo view. There is no navigation property from VesselView back to GroupVessel as there is no need to traverse the graph that way in the application.

Eirik.bell Eirik.bell · Accepted Answer · 2013-11-13T12:39:21

Finally figured it out, I used the wrong field as the foreign key field, changed to GroupId and it works

Entity Framework 4 - Many-To-Many Relationship with a view

1 Answers