Tag: entity framework

modelBuilder.Entity<Department>().Property(t => t.Name).IsRequired();

References
https://docs.microsoft.com/en-us/ef/ef6/modeling/code-first/fluent/types-and-properties#configuring-the-property-to-be-required

Configuring a Primary Key

modelBuilder.Entity<OfficeAssignment>().HasKey(t => t.InstructorID);

Configuring a Composite Primary Key

modelBuilder.Entity<Department>().HasKey(t => new { t.DepartmentID, t.Name });

References
https://docs.microsoft.com/en-us/ef/ef6/modeling/code-first/fluent/types-and-properties#configuring-a-primary-key

public class Student
{
    public int StudentId { get; set; }
    public string Name { get; set; }
}

public class Course
{
    public int CourseId { get; set; }
    public string CourseName { get; set; }
    public string Description { get; set; }
}

public class StudentCourse
{
    public int StudentId { get; set; }
    public Student Student { get; set; }

    public int CourseId { get; set; }
    public Course Course { get; set; }
}

public class Student
{
    public int StudentId { get; set; }
    public string Name { get; set; }

    public IList<StudentCourse> StudentCourses { get; set; }
}

public class Course
{
    public int CourseId { get; set; }
    public string CourseName { get; set; }
    public string Description { get; set; }

    public IList<StudentCourse> StudentCourses { get; set; }
}

public class SchoolContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("Server=.\\SQLEXPRESS;Database=EFCore-SchoolDB;Trusted_Connection=True");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<StudentCourse>().HasKey(sc => new { sc.StudentId, sc.CourseId });
    }
    
    public DbSet<Student> Students { get; set; }
    public DbSet<Course> Courses { get; set; }
    public DbSet<StudentCourse> StudentCourses { get; set; }
}

References
https://www.entityframeworktutorial.net/efcore/configure-many-to-many-relationship-in-ef-core.aspx

Installing the tools

dotnet ef can be installed as either a global or local tool.

dotnet tool install --global dotnet-ef

dotnet new tool-manifest # if you are setting up this repo
dotnet tool install --local dotnet-ef

Before you can use the tools on a specific project, you’ll need to add the Microsoft.EntityFrameworkCore.Design package to it.

dotnet add package Microsoft.EntityFrameworkCore.Design

Update the tools

Use dotnet tool update --global dotnet-ef to update the global tools to the latest available version. If you have the tools installed locally in your project use dotnet tool update dotnet-ef. Install a specific version by appending --version <VERSION> to your command. See the Update section of the dotnet tool documentation for more details.

Usefull Commands

dotnet ef database drop

Deletes the database.

dotnet ef database update

Updates the database to the last migration or to a specified migration.

dotnet ef dbcontext info

Gets information about a DbContext type.

dotnet ef dbcontext list

Lists available DbContext types.

dotnet ef dbcontext optimize

Generates a compiled version of the model used by the DbContext. Added in EF Core 6.

dotnet ef dbcontext scaffold

Generates code for a DbContext and entity types for a database. In order for this command to generate an entity type, the database table must have a primary key.

dotnet ef dbcontext script

Generates a SQL script from the DbContext. Bypasses any migrations.

dotnet ef migrations add

Adds a new migration.

dotnet ef migrations bundle

Creates an executable to update the database.

dotnet ef migrations list

Lists available migrations.

dotnet ef migrations remove

Removes the last migration, rolling back the code changes that were done for the latest migration.

dotnet ef migrations script

Generates a SQL script from migrations.

Reverting a Migration

Suppose you changed your domain class and created the second migration named MySecondMigration using the add-migration command and applied this migration to the database using the Update command. But, for some reason, you want to revert the database to the previous state. In this case, use the update-database <migration name> command to revert the database to the specified previous migration snapshot.

dotnet ef database update MyFirstMigration

The above command will revert the database based on a migration named MyFirstMigration and remove all the changes applied for the second migration named MySecondMigration. This will also remove MySecondMigration entry from the __EFMigrationsHistory table in the database.

Note: This will not remove the migration files related to MySecondMigration. Use the remove commands to remove them from the project.

References
https://docs.microsoft.com/en-us/ef/core/cli/dotnet