Mapping a foreign key with a custom column name

Question

I'm using Entity Framework 4.3 code-first with Oracle. I'm getting the following error:

System.InvalidOperationException : The ForeignKeyAttribute on property 'WidgetSequence' on type 'WidgetDistributor.WidgetEntity' is not valid. The foreign key name 'WIDGETSEQUENCE_ID' was not found on the dependent type 'WidgetDistributor.WidgetEntity'. The Name value should be a comma separated list of foreign key property names.

My entities are like this:

[Table("WIDGETENTITIES")] public class WidgetEntity {      [Column("WIDGETENTITY_ID")]     public int Id { get; set; }      [ForeignKey("WIDGETSEQUENCE_ID")]     public WidgetSequence Sequence { get; set; }      // and other properties that map correctly }  [Table("WIDGETSEQUENCES")] public class WidgetSequence {       [Column("WIDGETSEQUENCE_ID")]     public int Id { get; set; }      [Column("NUMBER")]     public int Number { get; set; } } 

My code seems correct. What have I done wrong, here?

Answer 1

If you don't want to use fluent syntax, there are three other ways of implementing the reference using data annotations (Personally I prefer data annotations as they seem easier to read and are written just above the property they are affecting):

1.1) Use ForeignKey (with an associated property) - version 1

[Table("WIDGETENTITIES")] public class WidgetEntity {      [Column("WIDGETENTITY_ID")]     public int Id { get; set; }      [Column("WIDGETSEQUENCE_ID")]     public int WidgetSequenceId { get; set; }      [ForeignKey("WidgetSequenceId")] //Has to be a property name, not table column name     public WidgetSequence Sequence { get; set; }      // and other properties that map correctly }  [Table("WIDGETSEQUENCES")] public class WidgetSequence {       [Column("WIDGETSEQUENCE_ID")]     public int Id { get; set; }      [Column("NUMBER")]     public int Number { get; set; } } 

1.2) Use ForeignKey (with an associated property) - version 2

[Table("WIDGETENTITIES")] public class WidgetEntity {      [Column("WIDGETENTITY_ID")]     public int Id { get; set; }      [ForeignKey("Sequence")] //Has to be a property name, not table column name     [Column("WIDGETSEQUENCE_ID")]     public int WidgetSequenceId { get; set; }      public WidgetSequence Sequence { get; set; }      // and other properties that map correctly }  [Table("WIDGETSEQUENCES")] public class WidgetSequence {       [Column("WIDGETSEQUENCE_ID")]     public int Id { get; set; }      [Column("NUMBER")]     public int Number { get; set; } } 

2) You can also use the InversePropertyAttribute.

[Table("WIDGETENTITIES")] public class WidgetEntity {      [Column("WIDGETENTITY_ID")]     public int Id { get; set; }      [InverseProperty("WidgetEntities")]     public WidgetSequence Sequence { get; set; }      // and other properties that map correctly }  [Table("WIDGETSEQUENCES")] public class WidgetSequence {       [Column("WIDGETSEQUENCE_ID")]     public int Id { get; set; }      [Column("NUMBER")]     public int Number { get; set; }      public virtual List<WidgetEntity> WidgetEntities { get; set; } } 

Answer 2

ForeignKey attibute expects a property name in your class as the argument but you given the column name. Use fluent mappings.

protected override void OnModelCreating(DbModelBuilder modelBuilder) {      modelBuilder.Entity<WidgetEntity>()      .HasRequired(w => w.Sequence)      .WithMany()      .Map(m => m.MapKey("WIDGETSEQUENCE_ID")); }