CODEWITHSUNDEEP
c#entity-frameworkdata-annotations
Alexander Olson
Alexander Olson

Reputation: 35

Requiring Unique Values in Entity Framework among items that share a common property value

I am trying to make the AnswerString required to be unique among answers that share the same ModuleID value. How would I go about achieving this? 

public class Answer
{
    public int AnswerID { get; set; }
    [MaxLength(25)]
    [Required]
    [Key]
    public string AnswerString { get; set; }
    public int ModuleID { get; set; }
    public int PictureCount { get; set; }
}

Upvotes: 2

Views: 108

Answers (2)

Anthony Mason
Anthony Mason

Reputation: 175

I would recommend making an attribute for the property which would evaluate at the class or property level. This would apply your business logic within the object/model and not rely on EF. If your intent is not to do as such, then I recommend the attributes suggested above or applying a constraint on the table itself.

Upvotes: 0

Ryan Bennett
Ryan Bennett

Reputation: 3432

Add this attribute to AnswerString:

[Index("IX_AnswerStringModuleId",2,IsUnique = true)]

Then add this attribute to ModuleId:

[Index("IX_AnswerStringModuleId",1, IsUnique = true)]

Basically this sets up a unique constraint where the combo of ModuleId and AnswerString must be unique.

See this answer as well: Unique Key constraints for multiple columns in Entity Framework

Upvotes: 2

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