Entity Framework Code-First（10）：Fluent API

Fluent API in Code-First:

We have seen different DataAnnotations attributes in the previous sections to override default Code-First Conventions. Here, we will learn about Fluent API.

Fluent API is another way to configure your domain classes. Fluent API provides more functionality for configuration than DataAnnotations. Fluent API supports the following types of mappings.

Mappings	To Database
Model-wide Mapping	Set default Schema Set Custom Convetions
Entity Mapping	To Single or Multiple Tables and Schema To Complex type Inheritance Hierarchies
Property Mapping	To Column, Column Name, Column Type, Nullable or Not Null Column, Column size, Columns Order To Concurrency column To Foreign key column To configure relationships

Let's get started with Fluent API. First of all, let's create Student & Standard domain classes and context class as we have created in the Simple Code-First Example section. Now, override OnModelCreating method of DBContext in a context class, as shown below.

public class SchoolContext: DbContext 
{
    public SchoolDBContext(): base() 
    {
    }

    public DbSet<Student> Students { get; set; }
    public DbSet<Standard> Standards { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Configure domain classes using modelBuilder here

        base.OnModelCreating(modelBuilder);
    }
}

Now, all your configuration code using Fluent API should be in OnModelCreating method. DbModelBuilder is a main class on which you can configure all your domain classes because at this point, all your domain classes would have initialized.

You can also use DataAnnotation and Fluent API at the same time. Code-First gives precedence to Fluent API > data annotations > default conventions.

DbModelBuilder class includes important properties and methods to configure. Visit MSDN for more information on DbModelBulder class.

Let's start to configure entities using Fluent API in the next section.