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Update intro.md

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Rick Anderson 2018-08-30 12:44:35 -07:00 committed by GitHub
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@ -108,7 +108,7 @@ Create a *Models* folder. In the *Models* folder, create a class file named *Stu
The `ID` property becomes the primary key column of the database (DB) table that corresponds to this class. By default, EF Core interprets a property that's named `ID` or `classnameID` as the primary key. In `classnameID`, `classname` is the name of the class. The alternative automatically recognized primary key is `StudentID` in the preceding example.
The `Enrollments` property is a navigation property. Navigation properties link to other entities that are related to this entity. In this case, the `Enrollments` property of a `Student entity` holds all of the `Enrollment` entities that are related to that `Student`. For example, if a Student row in the DB has two related Enrollment rows, the `Enrollments` navigation property contains those two `Enrollment` entities. A related `Enrollment` row is a row that contains that student's primary key value in the `StudentID` column. For example, suppose the student with ID=1 has two rows in the `Enrollment` table. The `Enrollment` table has two rows with `StudentID` = 1. `StudentID` is a foreign key in the `Enrollment` table that specifies the student in the `Student` table.
The `Enrollments` property is a [navigation property](/ef/core/modeling/relationship). Navigation properties link to other entities that are related to this entity. In this case, the `Enrollments` property of a `Student entity` holds all of the `Enrollment` entities that are related to that `Student`. For example, if a Student row in the DB has two related Enrollment rows, the `Enrollments` navigation property contains those two `Enrollment` entities. A related `Enrollment` row is a row that contains that student's primary key value in the `StudentID` column. For example, suppose the student with ID=1 has two rows in the `Enrollment` table. The `Enrollment` table has two rows with `StudentID` = 1. `StudentID` is a foreign key in the `Enrollment` table that specifies the student in the `Student` table.
If a navigation property can hold multiple entities, the navigation property must be a list type, such as `ICollection<T>`. `ICollection<T>` can be specified, or a type such as `List<T>` or `HashSet<T>`. When `ICollection<T>` is used, EF Core creates a `HashSet<T>` collection by default. Navigation properties that hold multiple entities come from many-to-many and one-to-many relationships.