Saturday, May 4, 2013

How to Use enum with Entity Framework 5 ?


What is enum ?
  • The enum keyword is used to declare an enumeration
  • A distinct type consisting of a set of named constants called the enumerator list
  • Every enumeration type has an underlying type
  • The default underlying type of the enumeration elements is int
  • By default, the first enumerator has the value 0
  • And the value of each successive enumerator is increased by 1
  • EF 5 enum can have the Types as  Byte, Int16, Int32, Int64 or SByte

Let's Take a Simple Example

E.g. 1 :

enum Days {Sat, Sun, Mon, Tue, Wed, Thu, Fri};

In this enumeration, Sat is 0, Sun is 1, Mon is 2, and so forth

E.g. 2 : Enumerators can have initializers to override the default values

enum Days {Sat=1, Sun, Mon, Tue, Wed, Thu, Fri};

In this enumeration, the sequence of elements is forced to start from 1 instead of 0


How to Use enum with Entity Framework 5 Code First ?
  • This feature is Latest improvement of EF 5

Step 1 : Open Visual Studio 2012

Step 2 : File ==> New Project as EF5EnumSupport

New Project as EF5EnumSupport


Step 3 :  Right Click Your Solution and then Click Manage NuGet Packages... 


Manage NuGet Packages



Step 4 : Click Online Tab and Then Type Entity Framework 5 on Search Box
            After that Select EntityFramework and Click Install 


Select EntityFramework

Step 5 : Click I Accept


Click I Accept


After the above Step, below mentioned DLLs (Red Color)  have added to the Project


DLLs (Red Color)  have added to the Project


Step 6 : Add ==> New Class and make it as enum Type Course

Course.cs
Complete project
 namespace EF5EnumSupport.Models
 {
    public enum Course
    {
        Mcsd = 1,
        Mcse,
        Mcsa,
        Mcitp
    }
 }

Step 7 : Add ==> New Class as Student

Student.cs

 namespace EF5EnumSupport.Models
 {
    public class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public Course Course { get; set; }
    }
 }

Step 8 : Create DbContext derived Class as StudentContext

StudentContext.cs

 using System.Data.Entity;

 namespace EF5EnumSupport.Models
 {
    public class StudentContext : DbContext
    {
        public DbSet<Student> Students { get; set; }
    }
 }

Step 9 : Console application's Main Method is as below

Program.cs

using System;
using System.Linq;
using EF5EnumSupport.Models;

namespace EF5EnumSupport
{
  public class Program
  {
     static void Main(string[] args)
     {
       using (var context = new StudentContext())
       {
        context.Students.Add(new Student { Name = "Sampath Lokuge",
                                           Course = Course.Mcsd });
        context.SaveChanges();

         var studentQuery = (from d in context.Students
                             where d.Course == Course.Mcsd
                             select d).FirstOrDefault();

         if (studentQuery != null)
          {
           Console.WriteLine("Student Id: {0} Name: {1} Course : {2}",
                            studentQuery.Id, studentQuery.Name,
                            studentQuery.Course);
           }
         }
     }
  }
}

The brand new enum support allows you to have enum properties in your entity classes

enum properties in your entity classes


Step 10 : Run the Console Application
               
               DEBUG ==> Start Without Debugging (Ctrl + F5)

Run the Console Application


Step 11 :  Where's the Database ?
  • By default the database will be created on the LocalDB instance
  • The Entity Framework names the database after the fully qualified name of the derived context
  • i.e. EF5EnumSupport.Models.StudentContext

    SQL Server Object Explorer in Visual Studio 2012 is as below 

     
    SQL Server Object Explorer in Visual Studio 2012
 
          View Data on Students Table

View Data on Students Table

      
    What is LocalDb ?
  • Microsoft SQL Server 2012 Express LocalDB is an execution mode of SQL Server Express targeted to program developers
  • LocalDB installation copies a minimal set of files necessary to start the SQL Server Database Engine                        

That's It.You're Done.

DownloadEntity Framework 5














Conclusion
  • Entity Framework 5 brings a number of improvements and enum Support in Code First is one of them
  • You can see that when you use enum type with your model class, Visual Studio 2012 gives  intellisense support out of the box
  • It's really awesome new feature of the Entity Framework 5
  • Enjoy it

I hope this helps to You.Comments and feedback greatly appreciated.

If you feel it was a good article,Give me a +1.Thank You.





Happy Coding.


Another Article about Entity Framework 5

What is New in Entity Framework 5 ?

18 comments:

  1. nice and very detailed, are you into trainings, whats ur objective?

    ReplyDelete
    Replies
    1. Hi Ganesh,

      Thanks for your feedback.
      Actually My objective is learning latest things and share it with your'll.
      Now tech blogging has become my hobby :)

      Delete
  2. Nice post. Always attach sample project.

    ReplyDelete
    Replies
    1. Hi askarmus,

      Thanks, I’m glad you enjoyed it!

      Delete
  3. Cool post, thank. I know that EF is growing.

    Sent from LinkedIn for iPad

    -Mykhailo Basiuk-

    ReplyDelete
    Replies
    1. Hi Mykhailo,

      Thanks for your feedback.
      Keep in Touch.

      Delete
  4. Nice post and well explained... Thanks for sharing...

    ReplyDelete
    Replies
    1. Hi Safeer,

      Thanks,I’m glad you found it useful!

      Delete
  5. Thanks. It'is very good your explanation and examples.

    Congratulations!

    ReplyDelete
    Replies
    1. Hi Claudio,

      You're warmly welcome.
      Stay in touch.

      Delete
  6. Good One Sampath!!!
    keep posting more..

    ReplyDelete
    Replies
    1. Hi Priyanka,

      Glad to hear that it helped!
      Keep in Touch.

      Delete
  7. Very good update. I am always wondering about why we can't use C# expressions in LINQ to SQL queries. Now Enum support is very useful one. Thanks to author.

    ReplyDelete
    Replies
    1. Hi Mukesh,

      Thanks, I’m glad you enjoyed it!
      Keep in Touch.

      Delete
  8. If you modify the Student.cs file to have a collection of courses it does not work. Are enum collections not supported?

    public class Student
    {
    public Student()
    {
    this.Courses = new List();
    }

    public int Id { get; set; }
    public string Name { get; set; }
    public IList Courses { get; set; }
    }

    ReplyDelete
    Replies
    1. Hi Sammy,

      Yes.You're right.Entity Framework doesn't support having a collection of a Complex Type (such as enum) on an Entity type.
      So,I don't know exactly what you're trying to achieve by using this (i.e. Business scenario).If you could put more details about your scenario then may be I could give more support.

      Delete
  9. Replies
    1. Hi Satish,

      You're warmly welcome.
      Keep in Touch.

      Delete

Thanks for your Feedback.