Entity framework map one to one
In the database, this is represented with foreign keys, of course. Which one you drop is up to you. Then,.HasRequired Grade (s rrentGrade) specifies that the Student entity has required the CurrentGrade property.
Entries Executing a linq query against a DbSet In Entity Framework you commonly use navigation properties to load entities that are related to the returned entity by the defined association. You can have only one timestamp property in a given class. This kind of association is called a foreign key association. PartmentID partmentID; The following code removes a relationship by setting the foreign key to null.
This will result in a one-to-many relationship between the Students and Grades table in the database, where the Students table includes foreign key Grade_GradeId as shown below. The entities will appear like the diagram shown below: Learn how to configure a one-to-many relationship in the next section.
Public class Student public int Id get; set; public string Name get; set; public int? Code First maps this property to a non-nullable field in the database.
To do this just modify your model classes: public class Person public int PersonId get; set; public string Name get; set; public virtual ICollection Car Cars get; set; / don't forget to initialize (use HashSet) public class Car public int. Local veChanges tach tValidationErrors DbContext. This will create a NotNull foreign key column in the. Public class Student public int StudentId get; set; public string StudentName get; set; public class Grade public int GradeId get; set; public string GradeName get; set; public string Section get; set; After implementing the one-to-many relationship in the above.
It means that each Student entity points to a Grade. For information on setting up relationships in your model, see the following pages. The HasOptional method configures the Address navigation property in Student entity as optional (not required when saving the Student entity). EF forms One-to-One relationships on entities not in the.
Consider the following Student and Grade entity classes. They are in the database, but they are not foreign keys, as it might be expected. We will implement a one-to-Zero-or-One relationship between the following Student and StudentAddress entities.
The only real way to enforce this rule if the People and the Car tables have the 'same' primary key (same values in the connected records). So, we don't need to apply any attributes on it because EF will make the StudentId column as a PrimaryKey in the Students table in the database.