It's just here to add the class-level attribute.
Below is the partial class and MetadataType class that you need to create under the assumption you want to add DataAnnotations to the Person class’ FirstName field:
#Ef data annotations code
I know it’s hard to visualize by my typing this out in a paragraph, so I’ll give you code he gave me. This MetadataType class, that corresponds to a single entity class, is applied to the partial class you manually created, which then links everything up. The trick here, as Austin points out, is to use a MetadataType class that holds the DataAnnotations. Now, can we just annotate the fields straight up in the partial class we manually create? Well, not directly. This gets us around the problem of the regenerating entities wiping out any DataAnnotations, since partial classes we create manually aren’t regenerated by the T4 template that creates the entities. This means that you can extend them by creating another partial class for each of the entity classes. See, when you generate entities, they are created as partial classes. I recently asked this question on StackOverflow, and Austin Lamb of the Microsoft Silverlight team was kind enough to let me know how this is done in the Silverlight world, which ended up working seamlessly with MVC. Since entities are regenerated often (meaning annotating the entities directly will result in your changes being wiped out pretty quickly), but are the preferred way of working with databases, what’s the best way to go about annotating the entities so they work seamlessly in the MVC framework? Here’s an example of the DataAnnotations in a typical model: public class LogOnModel The problem with this is that entity models are dynamically generated, and don’t contain annotations of their own. Now, though, I’m building a pretty big application that I’ll be putting out for a longer term, and will use SQL Server for the back-end with Entity Framework 4.0 entities as my model. With these, you can use the to decorate your classes with validation, labels, datatypes, field types and more that are used in MVC views to dynamically create your UI. Previously, I’ve just used regular old objects like are in the starter projects to play around with my applications as the “M” in my MVC.
I’ve not used MVC to build a production app until now, and it’s been killer fast building things out quickly. This configuration should be done in the Context class.I’ve been working with MVC3 and Razor lately.
#Ef data annotations how to
Now that we have seen how to configure the generation of a database with DataAnnotation, we’ll see how to do the same, and more, with Declare a property as foreign key with Code Fluent Here is the first operation we can’t do using DataAnnotations. It asks us to specifyĪn action in case of delete (to avoid multiple cascade delete) or to modify our constraints.Īs we don’t want to modify our constraints, we will specify an action in case of delete. It estimates there will be some issues if we let it as is. It doesn’t want to create tables and constraints because This error doesn’t come from Entity Framework or Code First, it comes from SQL Server.
#Ef data annotations update
Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modifyĬould not create constraint. On table 'Tasks' may cause cycles or multiple cascade paths. Introducing FOREIGN KEY constraint 'FK_Tasks_Projects_ProjectId' Here is how to do it using DataAnnotations: So we will define a maxĪlso indicate that a project should have a name. It’s not really useful and we don’t want the Name of the project to be so long. The string type in our class are nvarchar(max). If we take a look at the table Project, we can see that all our columns created from Define MaxLength of a column using DataAnnotationįirst, we will define our columns. The first one is using Data Annotations as we have seen on my second post about foreign key relationships, In Code First, there are two ways for configuring database creation. Now that we have learnt how to create a database with Code First and howĪ foreign key relationship, let's see what else can be configured. In this article, we are going to see how to use Data Annotations and Code Fluent to tweak our database. In a second one, I explain how to declare foreign keys forĬode First: EF Code First: Add a foreign key relationship. How to generate a table using EF Code First. We saw in a first article, EF Code First: Let's try it,
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