Unique multiple column in EF6 codefirst

Question

I have a class email that looks like this:

public class Email
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public string Subject { get; set; }
    public string Body { get; set; }
    public string From { get; set; }
    public DateTime SentOn { get; set; }
    public List<string> To { get; set; }
}

To ensure uniqueness, I made a composite key on Subject, FromandSentOn

This created a problem in which if the object exceeds 128 characters, the check is not performed. So I just put an attribute on it [MaxLength]. But now it cannot be a key column

What should I do? Is there a way to ensure uniqueness without being a key?

Answer 1

If you use EF 6.1, you can use Features of several columns :

public class Email
{
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }
   [Index("IX_EmailUniqueness", 1, IsUnique = true)]
   public string Subject { get; set; }
   public string Body { get; set; }
   [Index("IX_EmailUniqueness", 2, IsUnique = true)]
   public string From { get; set; }
   [Index("IX_EmailUniqueness", 3, IsUnique = true)]
   public DateTime SentOn { get; set; }
   public List<string> To { get; set; }
}

Answer 2

SO, , EF FluentAPI Constraint API?

, EF6.1 . MSDN

EDIT:

msdn , , PK, - 900 , -.

4000, :

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