Entity Framework: Code First and Magic Unicorns

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  • EDMX. Entity Data Model. A representation of your classes in XML. Three files: Conceptual (Entity Model) CDSL. Logical (Database Model) SSDL Mapping (Between Entity and Database) MSL. EDMX -> In memory model and metadata. EF translates the XML into an memory model. It uses this model to persist and read data from the database.
  • Entity Framework: Code First and Magic Unicorns

    1. 1. Richie Rump @Jorrisswww.jorriss.net
    2. 2. • Object-Relational Mapping Framework• Allows developers to retrieve database data from an object model.• Converts object data into relational data• Uses your classes• Generates SQL
    3. 3. • Code First Model• DbContext• Fluent API
    4. 4. • Bug Fixes• Semantic VersioningBecause Entity Framework 4.2 is betterthan:Entity Framework 4.1 Service Pack 2Update 1 Refresh Release To Web Pack
    5. 5. • Code First Migrations• Data Annotations on non-public properties• Additional configuration file settings• Removal of EdmMetadata table• Bug Fixes
    6. 6. • Added –IgnoreChanges to enable CodeFirst against existing database.• More inevitable bug fixes.
    7. 7. EF 4.3.1 – Bug Fixes EF 4.3 - Migrations EF 4.2 – Bug FixesEF 4.1 - Code First & DbContext Entity Framework 4.0 included with .Net 4.0
    8. 8. Design First Code First Model First Code First Create .edmx model in designer Define classes & mapping in code New Generate DB from .edmx Database auto-created at Database Classes auto-generate from runtime .edmx Database First Code First Reverse engineer .edmx model Define classes & mapping in code Existing Classes auto-generate from Database .edmxAdapted from Programming Entity Framework: Code First by Julie Learman and Rowan Miller page 3.
    9. 9. Lovingly stolen from Programming Entity Framework: Code First by Julie Lerman and Rowan Miller page 9.
    10. 10. In a word: Nuget
    11. 11. • What does code look like?• How do we use it?• Stop! Demo time.
    12. 12. • Convention over configuration – Database naming – Primary Key• SQL Server Express – default database• dbContext Class
    13. 13. • It’s not enough to use convention.• Tells EF how to map the object model to the database model.• Place annotations directly against the property in your class.• System.ComponentModel.DataAnnotations
    14. 14. • Key – Defines a Primary Key• Column – Defines DB column name• Table – Defines table name for a class• Required – Defines a Required DB field• NotMapped – Property not in DB mapping• MinLength() – Min length for a property• MaximumLength() – Max length for property• Range() – Defines a valid value range
    15. 15. [Table(“Product_Order")]public class Order{ [Key] [Column("Order_ID")] public int OrderId { get; set; } public DateTime Date { get; set; } public OrderState State { get; set; } public string Item { get; set; } [Range(1, 25)] public int Quantity { get; set; } [MinLength(3, ErrorMessage="What are you thinking?")] [MaxLength(50, ErrorMessage="ERROR!! FAILZ!!!!")] public string Name { get; set; } [NotMapped] public string Note { get; set; }}
    16. 16. • Allows you to configure EF without polluting your classes with annotations.• Cleaner code• Can have all EF mapping code in one file.• Some things you can only do in the Fluent API
    17. 17. Data Annotations[Column("Order_ID")]public int Id { get; set; }Fluent APImodelBuilder.Entity<Order>() .Property(p => p.Id).HasColumnName("Order_ID");
    18. 18. • This time it will work…I swear!
    19. 19. • Expressed via the navigation properties in your classespublic class Order{ public int Id { get; set; } public OrderState State { get; set; }}
    20. 20. public class Order { public int Id { get; set; } public int OrderStateID { get; set; } public OrderState State { get; set; } }public class OrderState{ public int Id { get; set; }}public OrderConfiguration(){ ToTable("Order"); Property(p => p.OrderStateID).HasColumnName("Order_State_ID"); HasRequired(p => p.State).WithMany() .HasForeignKey(f => f.OrderStateID);}
    21. 21. public class Order { public int Id { get; set; } public int PersonID { get; set; } public virtual Person SalesPerson { get; set; } } public class Person { public int PersonID { get; set; } ... public List<Order> Orders { get; set; } }public OrderConfiguration(){ ToTable("Order"); Property(p => p.PersonID).HasColumnName("Person_ID"); HasRequired(p => p.SalesPerson).WithMany(t => t.Orders) .HasForeignKey(f => f.PersonID);}
    22. 22. public class Order{ public int Id { get; set; } ... public List<Item> Items { get; set; }}public class Item{ public int Id { get; set; } ... public List<Order> Orders { get; set; }}HasMany(p => p.Items).WithMany(t => t.Orders) .Map(m => { m.ToTable("Order_Item"); m.MapLeftKey("Order_ID"); m.MapRightKey("Item_ID"); });
    23. 23. • New way to interact with EF objects• Makes interaction with EF MUCH simpler• Encapsulates existing EF objects such as ObjectContext, ObjectSet and ObjectQuery
    24. 24. • DbContext – Provides facilities querying and persisting object changes.• DbSet – Represents an entity for CRUD operations• Change Tracker API and Validation API are other features
    25. 25. EFTestContext context = new EFTestContext();var query = context.Orders .Where(c => c.PersonID == 22) .Include(c => c.State) .ToList();List<Order> orders = context.Orders.ToList();
    26. 26. • Easy way to retrieve an object via the Primary Key.EFTestContext context = new EFTestContext();Person p = context.People.Find(1);
    27. 27. EFTestContext context = new EFTestContext();Person p = new Person { FirstName = "Testy", LastName = "User" };context.People.Add(p);context.SaveChanges();
    28. 28. EFTestContext context = new EFTestContext();Person p = context.People.Find(1);context.People.Remove(p);context.SaveChanges();
    29. 29. • Migrations is a new way to generate database changes automatically• It’s controlled through PowerShell commands• Can migrate forward or rollback DB changes.• Migrations can be handled automatically. EF will automatically apply change scripts
    30. 30. • To turn Migrations onPM> Enable-Migrations• This creates a Migration folder in project• Creates Configuration.cs file• Creates __MigrationHistory system table in DB
    31. 31. PM> Add-Migration "Inital" -IgnoreChanges• “Initial” is the name of the migration• The –IgnoreChanges switch tells EF to create an empty migration. Use this if this is the first migration and EF did not create the DB.• Creates a cs file with the changes since the last migration.• Does not apply changes to DB.
    32. 32. PM> Update-Database• Pushes the migration changes to the DB• Use the –script switch to have EF create a SQL script of the changes.• Use –TargetMigration to determine end point for DB. (Rollback/Forward)• Be careful. I wouldn’t run against a production DB.
    33. 33. Y U NO DO DATABASE RIGHT?!?!?!!!
    34. 34. • Now in beta• Install using Nuget Install-Package EntityFramework –Pre• ENUMS!• Performance Improvements• Spatial Data Types• Table-Valued Functions• Most features only in .Net 4.5
    35. 35. • Julie Lerman’s Blog http://thedatafarm.com/blog/• Rowan Miller’s Blog http://romiller.com• Arthur Vicker’s Blog http://blog.oneunicorn.com• #efhelp on twitter• StackOverflow (of course)• PluralSite – Julie Lerman’s EF videos
    36. 36. Richie Rump@Jorrisshttp://jorriss.nethttp://dotnetmiami.com

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