问题
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?
回答1:
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"));
}
回答2:
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; }
}
回答3:
There is a table called Users and it has a primary key called UserID.
There is another table called Directory, and it has a column called UserID which is defined as a foreign key to the Users table.
I'm able to use the ForeignKey annotation to map the foreign key like this:
[ForeignKey("xyzzy")]
public int? UserID { get; set; } // This is a column in the table
public virtual User xyzzy { get; set; } // This is my instance of User
来源：https://stackoverflow.com/questions/11148662/mapping-a-foreign-key-with-a-custom-column-name