Saturday, December 15, 2012

Entity Framework 6: Alpha2 Now Available

Entity Framework 6: Alpha2 Now Available:
The Entity Framework team recently announced the 2nd alpha release of EF6.   The alpha 2 package is available for download from NuGet. Since this is a pre-release package make sure to select “Include Prereleases” in the NuGet package manager, or execute the following from the package manager console to install it:
PM> Install-Package EntityFramework -Pre
This week’s alpha release includes a bunch of great improvements in the following areas:
  • Async language support is now available for queries and updates when running on .NET 4.5.
  • Custom conventions now provide the ability to override the default conventions that Code First uses for mapping types, properties, etc. to your database.
  • Multi-tenant migrations allow the same database to be used by multiple contexts with full Code First Migrations support for independently evolving the model backing each context.
  • Using Enumerable.Contains in a LINQ query is now handled much more efficiently by EF and the SQL Server provider resulting greatly improved performance.
  • All features of EF6 (except async) are available on both .NET 4 and .NET 4.5. This includes support for enums and spatial types and the performance improvements that were previously only available when using .NET 4.5.
  • Start-up time for many large models has been dramatically improved thanks to improved view generation performance.
Below are some additional details about a few of the improvements above:

Async Support

.NET 4.5 introduced the Task-Based Asynchronous Pattern that uses the async and await keywords to help make writing asynchronous code easier. EF 6 now supports this pattern. This is great for ASP.NET applications as database calls made through EF can now be processed asynchronously – avoiding any blocking of worker threads. This can increase scalability on the server by allowing more requests to be processed while waiting for the database to respond.
The following code shows an MVC controller that is querying a database for a list of location entities:
    public class HomeController : Controller
    {
        LocationContext db = new LocationContext();

        public async Task<ActionResult> Index()
        {
            var locations = await db.Locations.ToListAsync();

            return View(locations);
        }
    }
Notice above the call to the new ToListAsync method with the await keyword. When the web server reaches this code it initiates the database request, but rather than blocking while waiting for the results to come back, the thread that is processing the request returns to the thread pool, allowing ASP.NET to process another incoming request with the same thread. In other words, a thread is only consumed when there is actual processing work to do, allowing the web server to handle more concurrent requests with the same resources.
A more detailed walkthrough covering async in EF is available with additional information and examples. Also a walkthrough is available showing how to use async in an ASP.NET MVC application.

Custom Conventions

When working with EF Code First, the default behavior is to map .NET classes to tables using a set of conventions baked into EF. For example, Code First will detect properties that end with “ID” and configure them automatically as primary keys.
However, sometimes you cannot or do not want to follow those conventions and would rather provide your own. For example, maybe your primary key properties all end in “Key” instead of “Id”. Custom conventions allow the default conventions to be overridden or new conventions to be added so that Code First can map by convention using whatever rules make sense for your project.
The following code demonstrates using custom conventions to set the precision of all decimals to 5. As with other Code First configuration, this code is placed in the OnModelCreating method which is overridden on your derived DbContext class:
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Properties<decimal>()
                .Configure(x => x.HasPrecision(5));

        }
But what if there are a couple of places where a decimal property should have a different precision? Just as with all the existing Code First conventions, this new convention can be overridden for a particular property simply by explicitly configuring that property using either the fluent API or a data annotation.
A more detailed description of custom code first conventions is available here.

Community Involvement

I blogged a while ago about EF being released under an open source license.  Since then a number of community members have made contributions and these are included in EF6 alpha 2.
Two examples of community contributions are:
  • AlirezaHaghshenas contributed a change that increases the startup performance of EF for larger models by improving the performance of view generation. The change means that it is less often necessary to use of pre-generated views.
  • UnaiZorrilla contributed the first community feature to EF: the ability to load all Code First configuration classes in an assembly with a single method call like the following:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
       modelBuilder.Configurations
           .AddFromAssembly(
typeof(LocationContext).Assembly);

}
This code will find and load all the classes that inherit from EntityTypeConfiguration<T> or ComplexTypeConfiguration<T> in the assembly where LocationContext is defined. This reduces the amount of coupling between the context and Code First configuration classes, and is also a very convenient shortcut for large models.

Other upcoming features coming in EF 6

Lots of information about the development of EF6 can be found on the EF CodePlex site, including a roadmap showing the other features that are planned for EF6.
One of of the nice upcoming features is connection resiliency, which will automate the process of retying database operations on transient failures common in cloud environments and with databases such as the Windows Azure SQL Database.
Another often requested feature that will be included in EF6 is the ability to map stored procedures to query and update operations on entities when using Code First.

Summary

EF6 is the first open source release of Entity Framework being developed in CodePlex. The alpha 2 preview release of EF6 is now available on NuGet, and contains some really great features for you to try.
The EF team are always looking for feedback from developers - especially on the new features such as custom Code First conventions and async support. To provide feedback you can post a comment on the EF6 alpha 2 announcement post, start a discussion or file a bug on the CodePlex site.
Hope this helps,
Vihang
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