使用数据注释创建外键

Question

In the code below, I need to set a foreign key constrant on ParentInfoAddProperties.ParentQuestionAnswersId so that it is dependent on ParentQuestionAnswers.Id (which is a Primary Key). I am attempting to do so using data annotations but Entity Framework 6 wants to create a new Foreign Key column in my ParentQuestionAnswers table which references the ParentInfoAddProperties.Id column not the ParentInfoAddProperties.ParentQuestionAnswersId column. I do not want Entity Framework to create a new foreign key column.

I'd greatly appreciate if someone can explain what data annotations or (if necessary) fluent mappings I should specify to achieve the desired foreign key constrant. Thanks in advance.

namespace Project.Domain.Entities
{  
    public class ParentQuestionAnswers
    {
        public ParentQuestionAnswers()
        {
            ParentInfoAddProperties = new ParentInfoAddProperties();
        }

        [Required]
        public int Id { get; set; }

        [Required]
        public int UserId { get; set; }

        public ParentInfoAddProperties ParentInfoAddProperties { get; set; }
    }

    public class ParentInfoAddProperties
    {
        [Required]
        public int Id { get; set; }

        [Required]
        public int ParentQuestionAnswersId { get; set; }
    }
}

Answer 1

You could use the following data annotation, and use entity instead of int

[Required]
[ForeignKey("ParentQuestionAnswers")]
public ParentQuestionAnswers ParentQuestionAnswers { get; set; }

to get the Id only you could add the property

public int ParentQuestionAnswersId { get; set; }

but you still need the ParentQuestionAnswers property so EF will understand you .

(these code rows should be under the ParentInfoAddProperties class)

Answer 2

Add the

[KeyAttribute] 

to the Id column

http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.keyattribute(v=vs.110).aspx

and

[ForeignKeyAttribute]

to the ParentQuestionAnswersId property.

http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.schema.foreignkeyattribute.foreignkeyattribute(v=vs.110).aspx