One out of 2 properties should be null (EntityFramework Code First)

Question

I've searched a lot in the forum, but haven't found anything about regarding this issue.

I have 2 properties in the EntityFramework Code First:

    [Column(TypeName = "Money")]
    public decimal? Debit { get; set; }
    [Column(TypeName = "Money")]
    public decimal? Credit { get; set; }

One of them should be not null, but the other one should be null Examples:

Debit=null;
Credit=34;

Debit=45;
Credit=null;

On the other hand, it should not be possible to set both or none of them null. Is it possible to handle this issue with data annotations or should I solve it with a workaround?

Best regards!

Answer 1

You could always do the validation on the database side with a constraint,

ALTER TABLE TableName 
    ADD CONSTRAINT OneColumnNull CHECK 
    ((Debit IS NULL AND Credit IS NOT NULL) OR 
     (Debit IS NOT NULL AND Credit IS NULL)
    )

does exactly what you are looking for. You could just put that query as part of one of your database migration scripts.