Core data updating object
The Instructor entity has a nullable navigation property.The Entity Framework doesn't require you to add a foreign key property to your data model when you have a navigation property for a related entity.The attribute can also be used to generate default values, as in the case of database columns used to record the date a row was created or updated. The foreign key properties and navigation properties in the Course entity reflect the following relationships: A course is assigned to one department, so there's a type.But in this case you know that the column will be holding currency amounts, and the money data type is more appropriate for that.For example, when you fetch a course entity to edit, the Department entity is null if you don't load it, so when you update the course entity, you would have to first fetch the Department entity.
By using data annotation attributes, you can make one code change that will fix the display format in every view that shows the data.
attribute specifies that the caption for the text boxes should be "First Name", "Last Name", "Full Name", and "Enrollment Date" instead of the property name in each instance (which has no space dividing the words).
Notice that several properties are the same in the Student and Instructor entities.
When you're finished, the entity classes will make up the completed data model that's shown in the following illustration: In this tutorial, you: In this section you'll see how to customize the data model by using attributes that specify formatting, validation, and database mapping rules.
Then in several of the following sections you'll create the complete School data model by adding attributes to the classes you already created and creating new classes for the remaining entity types in the model.EF automatically creates foreign keys in the database wherever they're needed and creates shadow properties for them.