The Entity Framework Core Fluent API includes two IsRequired methods. One is available on the PropertyBuilder type and is applied to a property to configure the mapped database column as not nullable. In the example below, the Title property of the Book entity will be configured as not null. By default, strings are mapped to nullable columns in the database:
language-csharp
|
public class SampleContext : DbContext
{
public DbSet<Book> Books { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Book>()
.Property(b => b.Title)
.IsRequired();
}
}
public class Book
{
public int BookId { get; set; }
public string Title { get; set; }
public Author Author { get; set; }
}
The second IsRequired method is available on the ReferenceCollectionBuilder type and is applied to relationships to specify that they should not be optional. This option might be used to override the fact that by default, shadow property foreign keys are nullable:
language-csharp
|
public class SampleContext : DbContext
{
public DbSet<Book> Books { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Author>()
.HasMany(a => a.Books)
.WithOne(b => b.Author)
.IsRequired();
}
}
public class Author
{
public int AuthorId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public ICollection<Book> Books { get; set; }
}
public class Book
{
public int BookId { get; set; }
public string Title { get; set; }
public Author Author { get; set; }
}
Data Annotations
The Data Annotations equivalent for the IsRequired method is the Required attribute.
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