Setting unique Constraint with fluent API?
As an addition to Yorro's answer, it can also be done by using attributes.
Sample for int
type unique key combination:
[Index("IX_UniqueKeyInt", IsUnique = true, Order = 1)]
public int UniqueKeyIntPart1 { get; set; }
[Index("IX_UniqueKeyInt", IsUnique = true, Order = 2)]
public int UniqueKeyIntPart2 { get; set; }
If the data type is string
, then MaxLength
attribute must be added:
[Index("IX_UniqueKeyString", IsUnique = true, Order = 1)]
[MaxLength(50)]
public string UniqueKeyStringPart1 { get; set; }
[Index("IX_UniqueKeyString", IsUnique = true, Order = 2)]
[MaxLength(50)]
public string UniqueKeyStringPart2 { get; set; }
If there is a domain/storage model separation concern, using Metadatatype
attribute/class can be an option: https://msdn.microsoft.com/en-us/library/ff664465%28v=pandp.50%29.aspx?f=255&MSPPError=-2147217396
A quick console app example:
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity;
namespace EFIndexTest
{
class Program
{
static void Main(string[] args)
{
using (var context = new AppDbContext())
{
var newUser = new User { UniqueKeyIntPart1 = 1, UniqueKeyIntPart2 = 1, UniqueKeyStringPart1 = "A", UniqueKeyStringPart2 = "A" };
context.UserSet.Add(newUser);
context.SaveChanges();
}
}
}
[MetadataType(typeof(UserMetadata))]
public class User
{
public int Id { get; set; }
public int UniqueKeyIntPart1 { get; set; }
public int UniqueKeyIntPart2 { get; set; }
public string UniqueKeyStringPart1 { get; set; }
public string UniqueKeyStringPart2 { get; set; }
}
public class UserMetadata
{
[Index("IX_UniqueKeyInt", IsUnique = true, Order = 1)]
public int UniqueKeyIntPart1 { get; set; }
[Index("IX_UniqueKeyInt", IsUnique = true, Order = 2)]
public int UniqueKeyIntPart2 { get; set; }
[Index("IX_UniqueKeyString", IsUnique = true, Order = 1)]
[MaxLength(50)]
public string UniqueKeyStringPart1 { get; set; }
[Index("IX_UniqueKeyString", IsUnique = true, Order = 2)]
[MaxLength(50)]
public string UniqueKeyStringPart2 { get; set; }
}
public class AppDbContext : DbContext
{
public virtual DbSet<User> UserSet { get; set; }
}
}
On EF6.2, you can use HasIndex()
to add indexes for migration through fluent API.
https://github.com/aspnet/EntityFramework6/issues/274
Example
modelBuilder
.Entity<User>()
.HasIndex(u => u.Email)
.IsUnique();
On EF6.1 onwards, you can use IndexAnnotation()
to add indexes for migration in your fluent API.
http://msdn.microsoft.com/en-us/data/jj591617.aspx#PropertyIndex
You must add reference to:
using System.Data.Entity.Infrastructure.Annotations;
Basic Example
Here is a simple usage, adding an index on the User.FirstName
property
modelBuilder
.Entity<User>()
.Property(t => t.FirstName)
.HasColumnAnnotation(IndexAnnotation.AnnotationName, new IndexAnnotation(new IndexAttribute()));
Practical Example:
Here is a more realistic example. It adds a unique index on multiple properties: User.FirstName
and User.LastName
, with an index name "IX_FirstNameLastName"
modelBuilder
.Entity<User>()
.Property(t => t.FirstName)
.IsRequired()
.HasMaxLength(60)
.HasColumnAnnotation(
IndexAnnotation.AnnotationName,
new IndexAnnotation(
new IndexAttribute("IX_FirstNameLastName", 1) { IsUnique = true }));
modelBuilder
.Entity<User>()
.Property(t => t.LastName)
.IsRequired()
.HasMaxLength(60)
.HasColumnAnnotation(
IndexAnnotation.AnnotationName,
new IndexAnnotation(
new IndexAttribute("IX_FirstNameLastName", 2) { IsUnique = true }));
Here is an extension method for setting unique indexes more fluently:
public static class MappingExtensions
{
public static PrimitivePropertyConfiguration IsUnique(this PrimitivePropertyConfiguration configuration)
{
return configuration.HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute { IsUnique = true }));
}
}
Usage:
modelBuilder
.Entity<Person>()
.Property(t => t.Name)
.IsUnique();
Will generate migration such as:
public partial class Add_unique_index : DbMigration
{
public override void Up()
{
CreateIndex("dbo.Person", "Name", unique: true);
}
public override void Down()
{
DropIndex("dbo.Person", new[] { "Name" });
}
}
Src: Creating Unique Index with Entity Framework 6.1 fluent API