Setting unique Constraint with fluent API

Question

I m trying to build an EF Entity with Code First  and an EntityTypeConfiguration using fluent API  creating primary keys is easy but not so with a Unique Constraint  I was seeing old posts that suggested executing native SQL commands for this  but that seem to defeat the purpose  is this possible with EF6

User · Answer

coni2k  s answer is correct however you must add  StringLength  attribute for it to work otherwise you will get an invalid key exception  Example bellow     StringLength 65    Index  IX FirstNameLastName   1  IsUnique   true   public string FirstName   get  set      StringLength 65    Index  IX FirstNameLastName   2  IsUnique   true   public string LastName   get  set

User · Answer

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 lt Person gt          Property t   gt  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

User · Answer

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 lt User gt         HasIndex u   gt  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 lt User gt          Property t   gt  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 lt User gt          Property t   gt  t FirstName        IsRequired        HasMaxLength 60       HasColumnAnnotation          IndexAnnotation AnnotationName           new IndexAnnotation              new IndexAttribute  IX FirstNameLastName   1    IsUnique   true       modelBuilder       Entity lt User gt          Property t   gt  t LastName        IsRequired        HasMaxLength 60       HasColumnAnnotation          IndexAnnotation AnnotationName           new IndexAnnotation              new IndexAttribute  IX FirstNameLastName   2    IsUnique   true

User · Answer

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 amp 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 lt User gt  UserSet   get  set

User · Answer

Unfortunately this is not supported in Entity Framework  It was on the roadmap for EF 6  but it got pushed back  Workitem 299  Unique Constraints  Unique Indexes

User · Answer

modelBuilder Property x   gt  x FirstName  IsUnicode   IsRequired   HasMaxLength 50

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