The Entity Framework Core Fluent API HasAlternateKey method enables you to create an alternate key by placing a unique constraint (and therefore a unique index) on a property or properties other than those that form the primary key. This is typically done to help ensure the uniqueness of data.
language-csharp
|
public class SampleContext : DbContext
{
public DbSet<Applicant> Applicants { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Applicant>()
.HasAlternateKey(a => a.PassportNumber);
}
}
public class Applicant
{
public int ApplicantId { get; set; }
public string Name { get; set; }
public string PassportNumber { get; set; }
}
If more than one property takes part in the unique constraint (composite alternate key), they are specified as properties of an anonymous type:
language-csharp
|
public class SampleContext : DbContext
{
public DbSet<Applicant> Applicants { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Applicant>()
.HasAlternateKey(a => new { a.PassportNumber, a.CountryCode });
}
}
public class Applicant
{
public int ApplicantId { get; set; }
public string Name { get; set; }
public string PassportNumber { get; set; }
public string CountryCode { get; set; }
}
Data Annotations
There is no Data Annotation equivalent to the HasAlternateKey method.
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