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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
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Problem Someone asked how to do a Conditional Include a couple of days ago on StackOverflow. They wanted to query for some entity (lets say Movies) and eager load some related items (lets say Reviews) but only if the reviews match some criteria (i.e.
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While writing my tips series and writing EF controllers for MVC I found that I regularly wanted to create and attach a stub entity . Unfortunately it isn’t quite that simple, you have to make sure the entity isn’t already attached first, otherwise you’ll
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UPDATE: thanks Zeeshan for pointing out that by default only non-nullable columns end up in the key for view backed entities. Imagine this situation, you have a view in your database, and it is updatable. Next you decide to use this view with the Entity
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Here’s a scenario which Damien and I encountered recently. We needed a way of specifying Facets for properties on Entities, i.e. things like Nullable , MaxLength , Precision etc. And we needed a class hierarchy because different types of properties have
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UPDATE: as Joe rightly points out in the comments (thanks Joe) when you try to pass a Func<T,V> to a method expecting Action<T> using lambda syntax it doesn't fail. Somehow the compiler must realize there is no match for Func<T,V> and
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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
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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
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As of right now Enums are not in EF4. Now we will be listening to your feedback about Beta1, and making some adjustments, so you never know, but at the moment it doesn’t look like they will be supported. Yesterday though I came up with a workaround that,
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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
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Background: In Tip 13 - How to Attach the easy way I showed you how to ‘establish’ the EntitySet for a particular CLR Type so you could Attach it. But in all the tips so far the same basic pattern is used: Attach the original version of the Entity Modify
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UPDATE: Made a couple of important corrections re-which Original Values are required. Problem: Imagine if you query blog posts: var myPosts = from post in ctx.Posts orderby post.Created descending select post; Just so you can output the post titles etc.
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The Problem: In some of earlier tips we talked about using Attach to load things into the ObjectContext in the unchanged state without wearing the cost of doing a query. Attach is the weapon of choice if performance is your goal. Unfortunately our APIs
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Hopefully if you're reading this you've noticed that I've started a series of Tips recently. The tips will mostly apply to Entity Framework or Data Services. Seeing as I expect to have a lots of tips, it probably makes sense to have some sort of index.
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Question: One of the questions you often see in the Entity Framework Forums is around sorting related items. For example imagine if you want to query customers, and return only those that have accounts more than 30 days in arrears, and at the same time
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