Entity Framework Core Generator - Generating a model from an existing database

November 14, 2018

Overview

.NET Core command-line (CLI) tool to generate Entity Framework Core model from an existing database.

• NuGet: https://nuget.org/packages/EntityFrameworkCore.Generator
• Source: http://github.com/loresoft/EntityFrameworkCore.Generator
• Documentation: https://efg.loresoft.com

Features

• Entity Framework Core database first model generation
• Safe regeneration via region replacement
• Safe Renaming via mapping file parsing
• Optionally generate read, create and update models from entity
• Optionally generate validation and object mapper classes

Documentation

Entity Framework Core Generator documentation is available via Read the Docs

Installation

To install EntityFrameworkCore.Generator tool, run the following command in the console

dotnet tool install --global EntityFrameworkCore.Generator

After the tool has been install, the efg command line will be available. Run efg --help for command line options

Generate Command

Entity Framework Core Generator (efg) creates source code files from a database schema. To generate the files with no configuration, run the following

efg generate -c <ConnectionString>

Replace <ConnectionString> with a valid database connection string.

Generation Output

The generate command will create the follow files and directory structure by default. The root directory defaults to the current working directory. Most of the output names and locations can be customized in the configuration file

Data Context Output

The EntityFramework DbContext file will be created in the root directory.

Entities Output

The entities directory will contain the generated source file for entity class representing each table.

Mapping Output

The mapping directory contains a fluent mapping class to map each entity to its table.

Initialize Command

The initialize command is used to create the configuration yaml file and optionally set the connection string. The configuration file has many options to configure the generated output. See the configuration file documentation for more details.

The following command will create an initial generation.yaml configuration file as well as setting a user secret to store the connection string.

efg initialize -c <ConnectionString>

When a generation.yaml configuration file exists, you can run efg generate in the same directory to generate the source using that configuration file.

Regeneration

Entity Framework Core Generator supports safe regeneration via region replacement and source code parsing. A typical workflow for a project requires many database changes and updates. Being able to regenerate the entities and associated files is a huge time saver.

Region Replacement

All the templates output a region on first generation. On future regeneration, only the regions are replaced. This keeps any other changes you’ve made to the source file.

Example of a generated entity class

public partial class Status
{
    public Status()
    {
        #region Generated Constructor
        Tasks = new HashSet<Task>();
        #endregion
    }

    #region Generated Properties
    public int Id { get; set; }

    public string Name { get; set; }

    public string Description { get; set; }

    public int DisplayOrder { get; set; }

    public bool IsActive { get; set; }

    public DateTimeOffset Created { get; set; }

    public string CreatedBy { get; set; }

    public DateTimeOffset Updated { get; set; }

    public string UpdatedBy { get; set; }

    public Byte[] RowVersion { get; set; }
    #endregion

    #region Generated Relationships
    public virtual ICollection<Task> Tasks { get; set; }
    #endregion
}

When the generate command is re-run, the Generated Constructor, Generated Properties and Generated Relationships regions will be replace with the current output of the template. Any other changes outside those regions will be safe.

Source Parsing

In order to capture and preserve Entity, Property and DbContext renames, the generate command parses any existing mapping and DbContext class to capture how things are named. This allows you to use the full extend of Visual Studio’s refactoring tools to rename things as you like. Then, when regenerating, those changes won’t be lost.

Database Providers

Entity Framework Core Generator supports the following databases.

• SQL Server
• PostgreSQL Coming Soon
• MySQL Coming Soon
• Sqlite Coming Soon

The provider can be set via command line or via the configuration file.

Set via command line

efg generate -c <ConnectionString> -p <Provider>

Set in configuration file

database:
  connectionString: 'Data Source=(local);Initial Catalog=Tracker;Integrated Security=True'
  provider: SqlServer

Database Schema

The database schema is loaded from the metadata model factory implementation of IDatabaseModelFactory. Entity Framework Core Generator uses the implemented interface from each of the supported providers similar to how ef dbcontext scaffold works.

View Models

Entity Framework Core Generator supports generating Read, Create and Update view models from an entity. Many projects rely on view models to shape data. The model templates can be used to quickly get the basic view models created. The model templates also support regeneration so any database change can easily be sync’d to the view models.