.NET/ASP.NET/C#/VB.NET PDF Document SDK

public string Description { get; set; } public decimal Price { get; set; } }

Customer myCustomer = dbContext.Customers.Single( cust => cust.CustomerID == 29531); Console.WriteLine(myCustomer.SalesOrderHeaders.Count);

8: Theming a Drupal Website . .................................................................. 173

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This fetches the entity for a specific customer, and then tries to get the number of SalesOrderHeader entities to which this item is related. Prior to .NET 4, this did not work it would print out 0, even though the example database has one related order for this customer. In .NET 3.5 SP1, the Entity Framework would initialize navigation properties such as the Customer object s SalesOrderHeaders property with an empty collection, and would load the related objects only if we ask it to, using the Load method shown in Example 14-7.

Again, the Spark view engine places no specific constraints on our model or our controller action, as shown in listing 10.13.

Customer myCustomer = dbContext.Customers.Single( cust => cust.CustomerID == 29531); myCustomer.SalesOrderHeaders.Load(); Console.WriteLine(myCustomer.SalesOrderHeaders.Count);

.NET 4 adds an alternative way to do this, called lazy loading. Rather than having to call Load explicitly, the EF can automatically load related objects at the point at which you access them. The context has a property to control this:

dbContext.ContextOptions.LazyLoadingEnabled = false;

public class ProductController : Controller { public ViewResult Index() Creates dummy { products var products = new[] { new Product { Name = "Toothbrush", Description = "Cleans your teeth", Price = 2.49m }, new Product { Name = "Hairbrush", Description = "Styles your hair", Price = 10.29m }, new Product { Name = "Shoes", Description = "Protects your feet", Price = 55.99m }, Sends products }; to the view return View(products); } }

Build first, then theme . ................................................................................................. 173 Using a Drupal theming framework: Fusion . .................................................................... 174 Installing Fusion core . ................................................................................................ 174 Installing a Fusion sub-theme ....................................................................................... 174 Install Skinr

This is true by default; setting it to false reverts to the pre-.NET 4 behavior. With this option switched on, Example 14-6 is equivalent to Example 14-7, because the EF will call Load for us when we first try to use the navigation property. (The collection ignores calls to Load if the entities are already loaded, so requesting multiple loads is not a problem.) In either case, the EF has to make an extra trip to the database. The call to Single will fetch the customer from the database before returning, which means that a second request is required when we later ask it (either explicitly or implicitly) to fetch the related rows, because the EF didn t know we were going to use these items until we asked for them. This might not be a problem, but in general, the more trips you make to the database, the slower things go.

Be wary of enabling lazy loading, because it can sometimes result in a lot of unnecessary database requests. For example, one author was involved with a project that had some diagnostic code that helpfully wrote a snapshot of certain objects into a log, including the value of all their properties. Unfortunately, this code was recursive if a property referred to another object, it would display that too, and if a property referred to a collection of objects, it would show all of them. This logging code had cycle detection, so it wouldn t get stuck in an infinite loop, but otherwise it wouldn t stop until it had showed every object reachable from the starting point. Unfortunately, lazy loading was enabled, so when this code was given an entity, it ended up fetching all entities that were related, no matter how distantly, to the first object at hand, so it hammered the database with thousands of requests each time a log entry was generated. Modern databases are surprisingly fast it s possible for this sort of problem to go unnoticed on development machines with their own local database instance. But you probably don t want it happening on a busy live server.

We provide only a dummy list of products for our Spark views to display. To create our Spark views, we use a folder structure similar to our structure for other view engines. In the root Views folder, we create a Product folder to correspond to our ProductController. Additionally, we create Layouts and Shared folders, as shown in figure 10.3. In Spark, view files use the .spark file extension. This is mainly so that the file extension doesn t conflict with other view engines in the IDE or at runtime. Spark supports the concept of layouts, which is equivalent to master pages. By convention, the default layout name is Application.spark, found in either the Layouts or Shared folder. To start on our layout, we ll create a text file in Visual Studio named Application.spark (instead of a Web Form or other template). This is shown in figure 10.4.