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An office asment only exists in relation to the instructor it's ased to, and therefore its primary key is also its foreign key to the Instructor entity. String maxLength: 50 ; When the Seed method runs, it will insert rows in the Department table and it will relate existing Course rows to those new Department rows. 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.
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Schema and add the column name attribute to the FirstMidName property, as shown in the following highlighted code: using System; using System. InstructorID, cascadeDelete: true.
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Add code to database context Next you'll add the new entities to the SchoolContext class and customize some of the mapping using fluent API calls. You could also add the list initialization to the constructor.
The DatabaseGenerated Attribute The DatabaseGenerated attribute with the None parameter on the CourseID property specifies that primary key values are provided by the user rather than generated by the database. DAL; using System; using System.
Models; using ContosoUniversity. If you changed data studetn was created by the Seed method, that will be changed back to its original state because of the AddOrUpdate method that you're using in the Seed method. Foreign Key and Properties The foreign key and properties reflect the following relationships: A department may or may not have an administrator, and an administrator is always an instructor. If you get migration errors you can't resolve, you can either change the database name in the connection string or delete the flr.
The DataType attributes do not provide any validation.
But in this case you know that the column will be holding currency amounts, and the money data type is more appropriate for that. To see an example of how to do that, you'll add an attribute to the EnrollmentDate property in the Student class. OfficeAsment' and 'ContosoUniversity. If that fails, another thing you can try is re-initialize the database by entering the following command in the PMC: update-database -TargetMigration:0 Open the database in Server Explorer as you did earlier, and expand the Tables node to see that all of the tables have been created.
Stjdent update-database command ran that code.
Therefore it has only a get accessor, and no FullName column will be generated in the database. This means that the Enrollment table contains additional data besides foreign keys for the ed tables in this case, a primary key and a Grade pooking. When you click Create, client side validation shows an error message: The field LastName must loking a string with a maximum length of Therefore have to change the code to give the new column a default value, and create a stub department named "Temp" to act as the default department.
You could put ror [Required] attribute on the Instructor property to specify that there must be a related instructor, but you don't have to do that because the InstructorID foreign key which is also the key to this table is non-nullable.
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As a result, existing Course rows will all be related to the "Temp" department after the Up method runs. The changes are highlighted. CourseID, t. An instructor can teach any of courses, so Courses is defined as a collection of Course entities. Suppose you want to ensure that users don't oooking more than 50 characters for a name. The DataType Attribute Pooking student enrollment dates, all of the web s currently display the time along with the date, although all you care about for this field is the date.
CourseID, s ; context.
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Run the Student Index again and notice that times are no longer displayed for the enrollment dates. The timestamp prepended to the migrations file name is used by Entity Framework to order the migrations.
CourseID, cascadeDelete: true. One-to-one studemt have a reference property in each class to the other class. AddColumn "dbo. In the Student. In that case, it would correspond to a many-to-many table without payload or a pure table in the database, and you wouldn't have to create a model class for it at all.
Code First migrations and deployment Customize the data model In this section you'll see how to customize the data model by using attributes that specify formatting, validation, and database mapping rules. You can also make database mapping changes using the Fluent APIas you'll see later in this tutorial. To make this mapping, you can use the Column attribute.
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The sudent image shows the original column name as it was before you applied the first two migrations. InstructorID, s ; context. Addressand a date selector can be provided for DataType.
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The Jvc Framework doesn't require you fof add a foreign key property to your data model when you have a property looing a related entity. If you didn't create an empty list, you wouldn't be able to add these relationships, because the Instructors property would be null and wouldn't have an Add method. This file contains code in the Up method that will update the database to match the current data model.
For more information, see this StackOverflow thread. You can relate them to the correct departments in the Seed method. InstructorID property as nullable, you'd get the following exception message: "The referential relationship will result in a cyclical reference that's not allowed. As was explained earlier, they are typically defined as virtual so that they can take advantage of an Entity Framework feature called lazy loading.
The DataType attribute can also enable the application to automatically provide type-specific features. The Column attribute specifies that when the database is created, the column of the Student table that maps to the FirstMidName property will be named FirstName. Entity relationship diagram The following illustration shows the diagram that the Entity Framework Power Tools create for the completed School model.
Enter the following commands in the Looming to create another migration: add-migration ColumnFirstName update-database In Server Explorer, open the Student table deer by double-clicking the Student table.
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Run the Createand enter either name longer than 50 characters. DataAnnotations; using System.
The StringLength attribute sets the maximum length in the database and provides client side and server side validation for ASP.