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.MapRightKey

Posted on 2014-02-23
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Last Modified: 2014-03-03
Trying to understand what the following code mean.... MapLeftKey???

Map(t => t.MapLeftKey("CourseID")
                 .MapRightKey("InstructorID")
                 .ToTable("CourseInstructor"));


using ContosoUniversity.Models;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;

namespace ContosoUniversity.DAL
{
   public class SchoolContext : DbContext
   {
      public DbSet<Course> Courses { get; set; }
      public DbSet<Department> Departments { get; set; }
      public DbSet<Enrollment> Enrollments { get; set; }
      public DbSet<Instructor> Instructors { get; set; }
      public DbSet<Student> Students { get; set; }
      public DbSet<OfficeAssignment> OfficeAssignments { get; set; }

      protected override void OnModelCreating(DbModelBuilder modelBuilder)
      {
         modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

         modelBuilder.Entity<Course>()
             .HasMany(c => c.Instructors).WithMany(i => i.Courses)
             .Map(t => t.MapLeftKey("CourseID")
                 .MapRightKey("InstructorID")
                 .ToTable("CourseInstructor"));
      }
   }
}
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Question by:yguyon28
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2 Comments
 

Author Comment

by:yguyon28
ID: 39881239
modelBuilder.Entity<Course>()
             .HasMany(c => c.Instructors).WithMany(i => i.Courses)
             .Map(t => t.MapLeftKey("CourseID")
                 .MapRightKey("InstructorID")
                 .ToTable("CourseInstructor"));

Does this actually create a table CourseInstructor?
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LVL 64

Accepted Solution

by:
Fernando Soto earned 1500 total points
ID: 39881253
Hi yguyon28;

This is building a many-to-many relationship from the Course table, the LeftKey, to a juction table called CourseInstructor, created in the database only, to the Instructor table, the RightKey side.

modelBuilder
    // Defines the table we are defining
    .Entity<Course>()
    // Course has a collection called Instructors and that Instructor has a collection of Courses.
    .HasMany(c => c.Instructors).WithMany(i => i.Courses)
    // The next three statements define the Juction table
    // The first entry in the table is the primary key from Course table identified as MapLeftKey
    .Map(t => t.MapLeftKey("CourseID")
    // The second entry in the table is the primary key from Instructor table identified as MapRightKey    
    .MapRightKey("InstructorID")
    // This is the table name for the junction table
    .ToTable("CourseInstructor"));
  

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