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C# Entity Framework Basics Extending Our Entity Data Model Using the Fluent API

Posted by Lee Puckett
Lee Puckett
12,539 Points

In Context.cs use the Fluent API in the OnModelCreating method to configure the CourseStudent.Grade property to have a p

I tried to copy his method for this challenge but I keep getting an error message. Not sure what I'm doing wrong.

Context.cs 
using System.Data.Entity;

namespace Treehouse.CodeChallenges
{
    public class Context : DbContext
    {
        public Context()
        {
            Database.SetInitializer(new DropCreateDatabaseAlways<Context>());
        }

        public DbSet<Course> Courses { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
            modelBuilder.Conventions.Remove<DecimalPropertyConvention>();
            modelBuilder.Conventions.Add (new DecimalPropertyConvention)(4, 3);

            modelBuilder.Entity<CourseStudent.Grade>()
            .Property(cb => cb.AverageRating)
            .HasPrecision(4, 3);

        }
    }
}

4 Answers

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

Here's a few hints:

  • for best results with challenges, do only what the challenge asks
  • challenges will generaly not be exactly like a video example
  • the challenge did not ask for any changes to Conventions
  • be sure the type argument to Entity is an entity and not a property
  • be sure to access the correct property via the "Property" method
Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

Closer, but still a couple of issues remain:

  • be sure the type argument to Entity is an entity and not a property

modelBuilder.Entity<CourseStudent.Grade>() :point_left: "CourseStudent" is the entity, "Grade" is the property

  • be sure to access the correct property via the "Property" method

.Property(cb => cb.AverageRating) :point_left: the property needed here is not "AverageRating"

Lee Puckett
Lee Puckett
12,539 Points
Lee Puckett
Lee Puckett
12,539 Points

Okay I took away the unnecessary code but still get the error "Did you call the model builder's 'Entity' method?"

using System.Data.Entity;

namespace Treehouse.CodeChallenges { public class Context : DbContext { public Context() { Database.SetInitializer(new DropCreateDatabaseAlways<Context>()); }

    public DbSet<Course> Courses { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
    modelBuilder.Entity<CourseStudent.Grade>()
        .Property(cb => cb.AverageRating)
        .HasPrecision(4, 3);
    }
}

}

Tanmoy Chowdhury
Tanmoy Chowdhury
12,622 Points
Tanmoy Chowdhury
Tanmoy Chowdhury
12,622 Points

Context.cs

using System.Data.Entity;

namespace Treehouse.CodeChallenges
{
    public class Context : DbContext
    {
        public Context()
        {
            Database.SetInitializer(new DropCreateDatabaseAlways<Context>());
        }

        public DbSet<Course> Courses { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
        modelBuilder.Entity<CourseStudent>().Property(c => c.Grade).HasPrecision(4,3);
        }
    }
}