Configure One-to-One relationship in Code First Entity Framework
Entity Framework (EF) is an Object Relational Mapper (ORM) that One thing I' ve learned is to let Entity Framework manage the entity If I want a property in my entity to be required, I can configure it with the Fluent API in the. EF Code First supports and relationships. The latter is what you are looking for ("one to zero-or-one"). Your attempts at fluent are saying required on. Learn how to configure a one-to-one relationship using Fluent API in Entity Framework Core.
So, apply [ForeignKey "Student" ] on the StudentAddressId property which will make it a foreign key for the Student entity, as shown below. Student includes the StudentAddress navigation property and StudentAddress includes the Student navigation property.
With the one-to-zero-or-one relationship, a Student can be saved without StudentAddress but the StudentAddress entity cannot be saved without the Student entity. EF will throw an exception if you try to save the StudentAddress entity without the Student entity. The HasOptional method configures the Address navigation property in Student entity as optional not required when saving the Student entity.
Then, the WithRequired method makes the Student navigation property of StudentAddress as required required when saving the StudentAddress entity; it will throw an exception when the StudentAddress entity is saved without the Student navigation property.
Configure One-to-Many Relationship in Entity Framework 6
Thus, you can configure a one-to-Zero-or-one relationship between two entities where the Student entity can be saved without attaching the StudentAddress object to it but the StudentAddress entity cannot be saved without attaching an object of the Student entity.
This makes one end required. EF API will create the following tables in the database. Configure a One-to-One relationship using Fluent API We can configure a one-to-One relationship between entities using Fluent API where both ends are required, meaning that the Student entity object must include the StudentAddress entity object and the StudentAddress entity must include the Student entity object in order to save it.
These will always be one-to-zero-or-one relationships. Address makes the Address property of StudentAddress as required and. All these we discussed in data annotations and here we will see how to achieve the same things using Fluent API. So rather than going into the domain classes to add these configurations, we can do this inside of the context.
The first thing is to override the OnModelCreating method, which gives the modelBuilder to work with. Default Schema The default schema is dbo when the database is generated. You can use the HasDefaultSchema method on DbModelBuilder to specify the database schema to use for all tables, stored procedures, etc. But if you want different table names then you can override this convention and can provide a different table name than the DbSet properties, as shown in the following code.
ToTable "StudentData" ; modelBuilder. ToTable "CourseDetail" ; modelBuilder. Entity Splitting Map Entity to Multiple Table Entity Splitting lets you combine data coming from multiple tables into a single class and it can only be used with tables that have a one-to-one relationship between them.
When the database is generated you see the following tables in your database as shown in the following image.
Properties Mapping The Property method is used to configure attributes for each property belonging to an entity or complex type. The Property method is used to obtain a configuration object for a given property. You can also map and configure the properties of your domain classes using Fluent API. But you can also override this convention, as shown in the following code. When the user specifies value longer than 24 characters, then the user will get a DbEntityValidationException exception.
Configure One-to-One Relationships using Fluent API in Entity Framework Core
HasDefaultSchema "Admin" ; modelBuilder. Similarly, Student EnrollmentDate is optional so we will be using IsOptional method to allow a null value in this column as shown in the following code.
By default, the Entity Framework uses the Code First conventions to map your classes to the database schema. If you use the Code First naming conventions, in most cases you can rely on Code First to set up relationships between your tables based on the foreign keys and navigation properties.
If they don't meet up with those conventions, there are also configurations you can use to impact relationships between classes and how those relationships are realized in the database when you're adding configurations in Code First.
Some of them are available in the data annotations and you can apply some even more complicated ones with a Fluent API.
Relationships - EF Core | Microsoft Docs
Configure One-to-One Relationship When you define a one-to-one relationship in your model, you use a reference navigation property in each class.
In database, both tables can have only one record on either side of the relationship. Each primary key value relates to only one record or no records in the related table. A one-to-one relationship is created if both of the related columns are primary keys or have unique constraints.
In a one-to-one relationship, the primary key acts additionally as a foreign key and there is no separate foreign key column for either table. This type of relationship is not common because most information related in this way would all be in one table. However, when both ends of the relationship are required or both sides are optional the Entity Framework cannot identify the dependent and the principal. When both ends of the relationship are required, you can use HasRequired as shown in the following code.
Configure One-to-Many Relationship The primary key table contains only one record that relates to none, one, or many records in the related table.