CHAPTER 8 ENTITY FRAMEWORK 190 (domain-driven design). I believe this release has resolved a number of the original concerns and introduced some great new features. Let’s see what they changed. EDM Designer Changes VS2010 contains a new Model Browser window that allows you to easily navigate your EDM (Figure 8-10). It is worth noting that previously in EF if an entity was removed from the model and subsequently brought back by using the wizard's update model functionality, then it would not be recreated. This was because a reference to the original object was still held in the CSDL file, so EF believed it still existed. In VS2010 the Model Browser window now contains a new facility that allows you to remove the CSDL entries as well. To do this, simply right-click on the item you want to remove under the Store node and select Delete. This will then remove the entity from the storage model. Figure 8-10. New model browser window CHAPTER 8 ENTITY FRAMEWORK 191 Performance The EF team has fine-tuned the performance of EF. One area that was improved is query generation. Previously parameter length was passed into queries. This was a bad decision; parameters could vary in length, which would prevent SQL Server from utilizing the query cache. In EF4 parameter length is no longer passed so the query cache can be utilized. The team has also tweaked how joins are made and removed unnecessary IsNull() calls. Pluralization Pluralization is a new feature in EF4 that generates more readable entity names. In EFv1 if you had a table called Film, then your entities would be called Film, and entity sets of Film would also be called Film, which made querying not as readable as it could be. Thus many developers would manually rename entity sets of Film to be called Films, which could be pretty boring. In EF4 if you select to use the pluralization option when creating the model, then Film’s entity set will be automatically named as Films. Note that the new pluralization feature doesn’t just stick an -s on the end of the table name. It is cleverer than that; for example, it knows when to append or remove -s, or when to modify the ending of a word to -ies (e.g., Category becomes Categories). Pluralization currently only works with U.S. English, although there is an option to override this and provide your own pluralization provider. The pluralization service is contained in System.Data.Entity.Design.dll (which is a shame as this would be useful elsewhere) and has a static method called CreateService(). For more information please see http://www.danrigsby.com/blog/index.php/2009/05/19/entity-framework-40- pluralization/. Deferred/Lazy Loading Lazy loading is a coding technique that minimizes resource usage and database access by not loading an entity until it is actually accessed. In EF4 lazy loading is switched on by default. If you want to turn lazy loading off, then set the ContextOptions.LazyLoadingEnabled option to false in the context class: ctx.ContextOptions.LazyLoadingEnabled = false; Eager Loading While we are looking at lazy loading it's worth mentioning its evil twin, eager loading. Eager loading is the exact opposite to lazy loading and means pre-loading an entity before you need it. This can increase the responsiveness of your application if the initialization is spread out over your application's lifetime. Julia Lerman has a great post that describes a number of ways to implement eager loading and measures the effect it has on performance: http://thedatafarm.com/blog/data-access/the-cost-of-eager- loading-in-entity-framework/. Complex Type Designer Support If your entities contain many fields then it can be useful to subdivide them into types. For example, a Patient entity in a medical system may have a huge amount of properties, but using complex types we could divide this information up like so: CHAPTER 8 ENTITY FRAMEWORK 192 Patient.Demographic.FirstName Patient.Demographic.Age Patient.Demographic.LastName Patient.Clinical.BloodType Patient.Financial.InsurerName Previously, if you wanted to accomplish this it was necessary to manually edit the CSDL, but as of EF4 you can accomplish this in the designer. Let’s see how to work with this feature with our Film entity. 1. Select the Film entity. 2. Hold down the Ctrl key and select the Description and Length properties (Figure 8-11). 3. Right-click and select the Refactor into New Complex Type option on the context menu. Figure 8-11. Refactoring description and Length into a complex type 4. VS will create a new property called ComplexProperty: rename this property to Detail. 5. If you open Program.cs you will now be able to access these properties using code similar to the following: Film Film = new Film(); Film.Detail.Description = "New film"; Film.Detail.Length = 200; CHAPTER 8 ENTITY FRAMEWORK 193 TIP To undo this change, remove the Film table from the model designer and then add it in again by right- clicking and selecting Update Model from Database. Complex Types from Stored Procedures The function import wizard will now create complex types from stored procedures. For example, let's imagine we wanted to add a method to our Film entity to return information about some of the crew, which is retrieved using the following stored procedure (mocked up for ease of use): CREATE PROCEDURE FilmGetCrewInfo @filmID int AS SELECT 'James Cameron' as Director, 'Arnold Schwarzenegger' as LeadActor1, 'Linda Hamilton' as LeadActor2 1. Go to the Model Browser window (tab next to Solution Explorer). 2. Right-click on the Complex Types folder and add a new complex type called FilmCrew. 3. Right-click on the newly created complex type and add three new string scalar properties called Director, LeadActor1, and LeadActor2 (Figure 8-12). Figure 8-12. Creating a new complex type 4. Open Chapter8.Model.edmx and on the designer surface right-click and select the Update Model from Database option. CHAPTER 8 ENTITY FRAMEWORK 194 5. Under the Stored Procedures node select the FilmGetCrewInfo stored procedure and click Finish. 6. Right-click on the designer surface and select AddFunction Import to bring up the screen shown in Figure 8-13. (I also clicked Get Column Information button when completed the other information to populate the stored procedure column information section). Figure 8-13. Add function import screen 7. Enter the function import name GetCrewInfo. 8. Select the stored procedure name FilmGetCrewInfo. 9. Select Complex in the Returns a Collection Of radio button options and then FilmCrew on the dropdown (notice how you have the option to create a complex type from the results of the stored procedure). 10. Click OK. The EF designer will now have added this function to the context where it can be accessed as follows (note you could then move this into your entity using partial classes): var crew = ctx.GetCrewInfo(1); Model Defined Functions Model defined functions allow you to define reusable functions at a model level. To create them at present you must modify the .edmx file directly, although this will probably change in future versions of CHAPTER 8 ENTITY FRAMEWORK 195 EF. In our convoluted example we will create a new property for our Film entity that will return the Film title and description separated by a space. 1. Right-click on the Chapter8Model.edmx file and select Open With. 2. Select XML Editor. 3. Find the following section: <edmx:ConceptualModels> <Schema Namespace="BookModel" Alias="Self" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns="http://schemas.microsoft.com/ado/2008/09/edm"> 4. Add the following inside the previous section: <Function Name="LongFilmDescription" ReturnType="Edm.String"> <Parameter Name="Film" Type="BookModel.Film"> </Parameter> <DefiningExpression> Trim(Film.Title) + " " + Film.Description </DefiningExpression> </Function> 5. Open Program.cs and add the following using directive: using System.Data.Objects.DataClasses; 6. Unfortunately LINQ to Entities doesn’t yet know about the LongFilmDescription function, so we have to tell it by creating a static class decorated with the [EdmFunction] attribute to allow us to access it. Add the following code in Program.cs. public static class MDF { [EdmFunction("BookModel", "LongFilmDescription")] public static string LongFilmDescription(Film f) { throw new NotSupportedException("This function can only be used in a query"); } } 7. Once this is done we can now utilize our function in L2E queries as follows: var query = from f in ctx.Films select new { FullName = MDF.LongFilmDescription(f) }; Model First Generation EF4 allows you to create your entity model in VisualStudio and use it to generate and update database structure. At the time of writing this works only with SQL Server. This facility is great for users unfamiliar with SQL or in situations where you do not have access to the database. 1. Create a new C# console project called Chapter8.ModelFirst. 2. Add a new ADO.NET Entity Data Model called CustomerModel. 3. Click Next. . xmlns:annotation="http://schemas.microsoft.com/ado/ 200 9 /02 /edm/annotation" xmlns="http://schemas.microsoft.com/ado/ 200 8 /09 /edm"> 4. Add the following inside the previous section:. CreateService(). For more information please see http://www.danrigsby.com/blog/index.php/ 200 9 /05 /19/entity-framework - 40 - pluralization/. Deferred/Lazy Loading Lazy loading is a coding technique that. see what they changed. EDM Designer Changes VS 201 0 contains a new Model Browser window that allows you to easily navigate your EDM (Figure 8- 10) . It is worth noting that previously in EF if