![]() ![]() As we've already covered, adding to our Item.Description entity property will cause it to be non-nullable. When we add a data annotation to the Item.Description property, we're creating a custom configuration for our entity property. Again, these defaults are more than sufficient - they are set up in order for our code-first migrations to set up conventional tables and columns as well as relationships within our MySQL database. There are also specific default configurations for primary keys (like Item.ItemId) and foreign keys (like Item.CategoryId). And usually those default configurations are sufficient! For example, the default configurations for our Item.Description entity property is for there to be a column called Description of type longtext that is nullable added to our Items table. The first thing to understand about entity properties is that EF Core handles creating all of the default configurations based on the code within our models. How Entity Properties Are Configured in our Database At the end of this lesson, we'll talk about the important takeaways. We'll also pause to look at the migration we create to see how to can verify how data annotations change our entity properties. However, to make this change reflected in our database, we need to create a migration and then update our database. ![]() This means that each entry in that table must have a value for that column, because the values for that column can't be null. When a database column is non-nullable, it means it can't be null, or have no value. In the case of Item.Description having the data annotation, this now updates our entity property to be non-nullable. That's right - data annotations can be used to configure our entities in code-first development with EF Core. Well, in the process of adding the validation attribute to the Item.Description property, we were also specifying how Item.Description as an entity property should be configured in our database. I connect to the SQL Server Express Edition through that window.Ģ) Now let me explain how EF knows how to build the tables, the columns, the data types and the various attributes (null, not null e.t.c).At the end of the lesson on model validation with validation attributes, we added two validation attributes to our Item model: we made the Item.Description property, and we set a between 1 and the integer's max value for the Item.CategoryId property. You can see this information through the VS 2012 IDE.Make sure you have opened the Server Object Explorer. Make sure you have a look at the tables and tables columns. A database is created and populated when the application runs.This happens through the magic of EF and Data Annotations.I launch SSMS connect to the instance of SQL Server 2012 Express and I browse to the database I have already installed SQL Server 2012 Express edition in my laptop. Public int TrainingDuration ġ) Make sure you run the application I mentioned earlier. I will use these two entity classes public class Footballer You can also do that imperatively using the Fluent API but this is beyond the scope of this post. We do add Data Annotations to our domain classes declaratively using attributes. With the database.For example it assumes that any property named ID represents the key property of the class.Data Annotations "live" inside the. The in-memory data that it needs to interpret the queries and interact EF Code FirstĪt run time, looks at the entity-domain classes and infers from them We can configure our domain-entity classes so that they can take bestĪdvantage of the EF.We can decorate our entity classes with declarativeĪttributes.Let me give you an insight on how EF Code First works. ![]() It will take some time to create this application but it is necessary in order to follow along. I will use another post also found in this blog to demonstrate Data Annotations.In order to fully understand what I am talking about, you need to read this post titled Using the Code First approach when building ASP.Net applications with Entity Framework. The last one (Code First) gains increasing popularity amongst developers. We have Database First,Model First and Code First. In this post I would like to talk about Data Annotations and how to use them in our Code First Entity framework applications.Developers use extensively EF to build their data access layer. ASP.NET 4.5 data annotations EF 5.0 Entity Framework ![]()
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