Relationships, navigation properties and foreign keys - EF6 | Microsoft Docs
You can't combine types in different contexts into one object graph. the multiple schema into one and push over to using a single DB context for the database. In a relational database, this is represented by a foreign key constraint. . more than one pair of navigation properties between two entity types. The Entity Framework Code First approach allows us to create a In the Code First approach, the database gets created from the classes. . create a public property of the generic DbSet type with domain entity passed in it.
Convention 3 Including navigation properties at both ends will also result in a one-to-many relationship, as shown below. Convention 4 A fully defined relationship at both ends will create a one-to-many relationship, as shown below.IQ 14: What are the types of database relationships?
This will create a one-to-many relationship with the NotNull foreign key column in the Students table, as shown below. If the data type of GradeId is nullable integer, then it will create a null foreign key. However, you may configure relationships using Fluent API at one place to make it more maintainable.
Configuring Entity Relationships with Entity Framework
Consider the following Student and Grade entity classes. First, we need to start configuring with any one entity class.
CurrentGrade specifies that the Student entity has required the CurrentGrade property. This will create a NotNull foreign key column in the DB. Now, it's time to configure the other end of the relationship - the Grade entity.
- Configuring Entity Relationships with Entity Framework
- Entity Framework - Relationships
Students specifies that the Grade entity class includes many Student entities. Entity framework supports three types of relationships, same as database: The following figure shows the visual designer for that EDM with all the entities and relationships among them.
Let's see how each relationship association is being managed by entity framework.
A student can have only one or zero addresses. Entity framework adds the Student reference navigation property into the StudentAddress entity and the StudentAddress navigation entity into the Student entity.
This means that Standard can have many Teachers whereas Teacher can associate with only one Standard. To represent this, the Standard entity has the collection navigation property Teachers please notice that it's pluralwhich indicates that one Standard can have a collection of Teachers many teachers.
Entity Framework Relationships
In a relational database, each entity such as the person, the school, the place of work is stored in separate tables and unique instances if the entity are identified by a Primary Key value. Relationships or associations between entities are defined in a database by the existence of Foreign Keys. One To Many The following diagram depicts a relationship between the Books and Authors tables in a database: Each table has a Primary Key PK that uniquely defines each instance of an entity or row within the table.
Book is the dependent entity in the relationship. It's integrity depends on a valid reference to an author. Author becomes the principal entity. Using foreign keys, you can link one author row in the database to many book rows.