Any Fluent API tutorials that use EF Database-First approach to explain the subject?

ef-database-first, entity-framework, fluent

Solution

There are no tutorials which would explain the Fluent API together with Database-First approach because Fluent API is made only for Code-First approach. You don't need the Fluent API if you want to create your model via Database-First.

Fluent API (together with Code-First data annotations and conventions) is a tool to define model details in code, such as string length, if a property is required or the type of relationship - many-to-many, one-to-many, etc. When using Database-First or Model-First the EDMX file has the same purpose - it contains all the details and mapping definitions of your model. Fluent API (+ data annotations and conventions) replaces the EDMX file only when using Code-First.

If you create the model via Database-First or Model-First, you will have an EDMX file representing your model. You can apply the T4 DbContext Generator to this EDMX file. The generated files have two characteristics being different from Code-First:

The generated connection string contains a section refering to the EDMX metadata which will be embedded into your assembly:

connectionString="metadata=res://*/Model.csdl
                          |res://*/Model.ssdl
                          |res://*/Model.msl;
                  ..."

The generated context `DbContext` will have an overridden `OnModelCreating` method which just throws an exception:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    throw new UnintentionalCodeFirstException();
}

As long as you leave the metadata section in the connection string, EF won't even call `OnModelCreating` or any code in Fluent API in this method. The metadata section tells EF that your model is DB- or Model-First and that the metadata are defined in the embedded EDMX and not in Fluent API.

However, you can remove the metadata section from the connection string, remove the `UnintentionalCodeFirstException` and write code with Fluent API in `OnModelCreating`. You can follow this procedure to create an initial model via Database-First and then build on this initial model for further development with Code-First.

At this point you are not working anymore with Database-First, but Code-First instead and everything you read about Fluent API is valid for you.

Problem

There are many tutorials on Fluent API, but they all explain it using Entity Framework Code-First code examples. Since I don't know Code-First, do you know of any Fluent API tutorials that would explain the subject using EF Database-First approach? Thank you

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