Over the last couple of years I’ve found myself in lots of situations where I’ve wanted to get ‘under the hood’ and see what is happening inside an IQueryable, but I haven’t had an easy solution, at least until now. Getting down and dirty like this is interesting because it means you can: Log...

In parts 1 thru 7 we made a Read / Write typed data service provider, although it was a little simplistic because it didn’t have relationships. So lets rectify that right now by adding a relationship to make this more 'real-world' Changes to our Classes If you remember from Part 3 we had just a Product...

In Tip 45 I showed you how to build a connection string at runtime, which is pretty nifty. The problem with that was that it relies on having metadata files (.csdl .ssdl and .msl) on local disk. But what if they live on a web-server or something and you don’t even have access to the local file...

Introduction Data Services sits above a Data Service Provider, which is responsible for interacting with the underlying Data Source on behalf of the Data Service. Data Services ships with some internal providers, and makes it possible for you to create custom providers too. So the obvious question...

Problem: Take this code: Category oldCategory = ctx.Categories .Include("Products") .First(c => c.Name == "Drink"); Category newCategory = new Category {Name = "Beverage"}; foreach(Product product in oldCategory.Products) { newCategory.Products.Add(product); } Ignore for a second that in...

This time a real simple one prompted by this question on StackOverflow. Problem: If you tell the Entity Framework about this class using Code-Only, by default every property becomes part of Entity, and as a result stored in the database. Usually this is what you want. But not always, imagine this class...

Background By default the Entity Framework embeds its metadata inside your assembly as a resource. It also puts a connection string in the App or Web Config that references those resources something like this: <add name="BloggingEntities" connectionString="metadata=res://*/Blogging.csdl|res://*/Blogging...

Background: When we give examples of how to use Code-Only we always start with a strongly typed Context derived from ObjectContext . This class is used to bootstrap the model. For example this (property bodies omitted for simplicity sake): public class MyContext : ObjectContext { public ObjectSet<Category>...

Sometimes you’ll find you need to issue a query or command that the Entity Framework can’t support. In fact this problem is common to most ORMs, which is why so many of them have a backdoor to the database. The Entity Framework has a backdoor too… .NET 3.5 SP1 In .NET 3.5 SP1 you can get to the underlying...

Problem: Imagine that you have these entities public class Product { public int ID { get; set; } public string Name { get; set; } public virtual Category Category { get; set; } } public class Category { public int ID { get; set; } public string Name { get; set; } public virtual List<Product> Products...

Scenario: In EF 4 we have FK relationships , available for the first time in .NET 4.0 Beta 2, so it is now possible to have a model something like this: public class Division { public int DivisionID {get;set} // Primary Key public string Name {get;set;} public virtual List<Lawyer> Lawyers {get;set;...

There have been lots of posts on the EFDesign blog talking about how the features in Code Only have evolved. But very little covering what we think will be the best way to write the code. You may have seen code like this: var prodConf = builder.Entity<Product>(); productConf.HasKey(p => p.Id...

Imagine that in your database you have a cascade delete on an FK relationship. Something like this: Here the Delete Rule says that when a Category is deleted all the related Products should be deleted too. If you generate an EF model from this database you get a model that on the surface looks no different...

We recently released a CTP that extends EF 4 Beta 1 which included Code Only. You can read more about Code Only here , here and here . If you look at the walkthroughs for Code Only you will see code that looks something like this: // Create a builder and configure it var builder = new ContextBuilder<MyContext>...

Imagine you want to write a query like this: var possibleBuyers= from p in ctx.People where p.Address.City == “Sammamish” && InMarketForAHouse(p) select p; Now theoretically this is possible so long as there is a SQL translation for InMarketForAHouse. In EF 4.0 you do this by creating a CLR stub...

Imagine you have a database function like the DistanceBetween function in Nerd Dinner : CREATE FUNCTION [dbo].[DistanceBetween]( @Lat1 as real, @Long1 as real, @Lat2 as real, @Long2 as real) RETURNS real AS BEGIN … END And you want to use it with the Entity Framework. Declaring the Function...

It is common to want to validate that your entities are ‘valid’ before you save them to the database. A naive form of validation might be to try to ensure that your entities are ‘valid’ before you add them to the context, but this doesn’t help you if you pass through ‘invalid’ states, i.e. as you build...

Short one this time. Craig Lee , a colleague of mine who works on the tools team, has just started blogging. He already has a number of posts, including an interesting one on keyboard shortcuts . Enjoy.

What are Stub Entities? A stub entity is a partially populated entity that stands in for the real thing. For example this: Category c = new Category {ID = 5}; is a stub entity. It has only the ID populated, which indicates this is a stub for Category 5. When are Stub Entities Useful...

For well over a year now I've been talking about how it is possible with EF to write a provider that sits between the EF and the native database provider. There are lots of reasons why you might do this. Here are some examples, you could write a: Tracing Provider Auditing Provider Caching Provider Query...

Sometimes rather than writing this: var customer = ctx.Customers.First(c => c.ID == 5); You would rather write something like this: var customer = ctx.Customers.GetCustomerById(5); In .NET 4.0 this would be trivial to do by modifying the T4 templates that do code gen. You would simply...

This is 22nd post in my ongoing series of Entity Framework Tips . If you want to do eager loading with the Entity Framework it is generally really easy, you simply write something like this: var results = from post in ctx.Posts.Include(“Comments”) where post.Author.EmailAddress == “alexj@microsoft...

This is 21st post in my ongoing series of Entity Framework Tips , and the first that is specific to EF 4.0. Entity Framework 4.0 Beta 1 As you’ve probably heard VS 2010 Beta 1 is now available to subscribers which means some of you can get your hands on EF 4.0 Beta 1 too. If you have any questions our...

This is 20th post in my ongoing series of Entity Framework Tips . Fixed Length Field Padding: If you have an fixed length column in the database, for example something like NCHAR(10) when you do an insert, padding happens automatically. So for example if you insert ‘12345’ you get 5 spaces automatically...

This is the 19th post in my ongoing series of Entity Framework Tips . Background: If you have a table with a timestamp column, and you reverse engineer an Entity from that table, you will end up with a Binary property in your entity (in my example called Version). If you look at the properties...