CODEWITHSUNDEEP
c#entity-frameworkforeign-keysone-to-many
A.D.
A.D.

Reputation: 1116

The ForeignKeyAttribute on property 'MyField' on type 'Class1' is not valid

Struggling on a Foreign key with Entity Framework (1 to many relationship).

class1:

 public partial class Class1
    {

        public int Id { get; set; }
       [ForeignKey("Class2_Id")]
        public Class2 Class2{ get; set; }
...}

Class2:
 public partial class Class2
    {

        public int Id { get; set; }
        public virtual ICollection<Class1> Stuff{ get; set; }
...}

1)I tried with fluentAPI: 1st try:

modelBuilder.Entity<Class2>().HasMany<Class1>(p => p.Stuff).WithOptional().Map(m => m.MapKey("Class2_Id")).WillCascadeOnDelete();

2nd try:

 modelBuilder.Entity<Class1>().HasRequired(i => i.Class2).WithMany().Map(m => m.MapKey("Class2_Id"));

2)without fluentAPI: I declared the concerned Class2 field this way:

[Column("Class2")]
public int Id { get; set; }

Even (which probably makes no sense):

[ForeignKey("Class2")]
public int Id { get; set; }

I always get this error:

The ForeignKeyAttribute on property 'Class2' on type 'Class1' is not valid. The foreign key name 'Class2_Id' was not found on the dependent type 'Class1'. The Name value should be a comma separated list of foreign key property names.

Any idea what is wrong?

thx in advance.

Upvotes: 1

Views: 363

Answers (1)

ocuenca
ocuenca

Reputation: 39376

With your fluent api configurations you are defining a unidirectional relationship, so the correct way would be:

modelBuilder.Entity<Class2>().HasMany(p => p.Stuff)
                             .WithOptional(c=>c.Class2)
                             .Map(m => m.MapKey("Class2_Id"))
                             .WillCascadeOnDelete();

MapKey method is used when you don't want to have the foreign key as a property in your model class.

Use ForeignKey attribute when you represent the FK column as a property of your entity:

public partial class Class1
{

    public int Id { get; set; }

    public int? Class2_Id{ get; set; }

    [ForeignKey("Class2_Id")]
    public Class2 Class2{ get; set; }
}

In this last case your relationship configuration using Fluent Api would be:

modelBuilder.Entity<Class2>().HasMany(p => p.Stuff)
                             .WithOptional(c=>c.Class2)
                             .HasForeignKey(c=>c.Class2_Id))
                             .WillCascadeOnDelete();

Upvotes: 1

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