Generate model from database using Entity Framework Power Tool

The software I am using are:

  • Microsoft Visual Studion 2013 Premium
  • Microsoft SQL Server 2012 Enterprise
  • Entity Framework 6.0.1
  • Entity Framework Power Tools 1.0
  • Windows Server 2008 R2

Create Database Objects

I created a test database with a table HR.Employees as the following in my local Microsoft SQL 2012 instance (full T-SQL script is here):

CREATE TABLE HR.Employees
(
  empid           INT          NOT NULL IDENTITY,
  lastname        NVARCHAR(20) NOT NULL,
  firstname       NVARCHAR(10) NOT NULL,
  title           NVARCHAR(30) NOT NULL,
  titleofcourtesy NVARCHAR(25) NOT NULL,
  birthdate       DATETIME     NOT NULL,
  hiredate        DATETIME     NOT NULL,
  address         NVARCHAR(60) NOT NULL,
  city            NVARCHAR(15) NOT NULL,
  region          NVARCHAR(15) NULL,
  postalcode      NVARCHAR(10) NULL,
  country         NVARCHAR(15) NOT NULL,
  phone           NVARCHAR(24) NOT NULL,
  mgrid           INT          NULL,
  CONSTRAINT PK_Employees PRIMARY KEY(empid),
  CONSTRAINT FK_Employees_Employees FOREIGN KEY(mgrid)
    REFERENCES HR.Employees(empid),
  CONSTRAINT CHK_birthdate CHECK(birthdate <= CURRENT_TIMESTAMP)
);

Reversed Engineering DB Objects to Classes

I created a simple C# console project called ‘EmployeeConsole’ in visual studio, which will create two files: Program.cs and App.config. Right Click on the project in Solution Explorer, and choose ‘Entity Framework – Reversed Engineering Code First’. Then connect to the instance (local) and database (test), and generate the model from test database for table ‘HR.Employees’.

What Does Entity Framework Power Tool Do?

1. Visual Studio first will install Entity Framework (runtime) into the project by creating packages.config as the following:

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="EntityFramework" version="6.0.1" targetFramework="net45" />
</packages>

2. Create model: a database context (testContext.cs)

using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using EmployeeConsole.Models.Mapping;

namespace EmployeeConsole.Models
{
    public partial class testContext : DbContext
    {
        static testContext()
        {
            Database.SetInitializer(null);
        }

        public testContext()
            : base("Name=testContext")
        {
        }

        public DbSet Employees { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new EmployeeMap());
        }
    }
}

3. Create model: a employees class in the model (Employee.cs)

using System;
using System.Collections.Generic;

namespace EmployeeConsole.Models
{
    public partial class Employee
    {
        public Employee()
        {
            this.Employees1 = new List();
        }

        public int empid { get; set; }
        public string lastname { get; set; }
        public string firstname { get; set; }
        public string title { get; set; }
        public string titleofcourtesy { get; set; }
        public System.DateTime birthdate { get; set; }
        public System.DateTime hiredate { get; set; }
        public string address { get; set; }
        public string city { get; set; }
        public string region { get; set; }
        public string postalcode { get; set; }
        public string country { get; set; }
        public string phone { get; set; }
        public Nullable mgrid { get; set; }
        public virtual ICollection Employees1 { get; set; }
        public virtual Employee Employee1 { get; set; }
    }
}

4. Create ORM: mapping POJO Employees class to physical table (EmployeeMap.cs) using Fluent API

using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.ModelConfiguration;

namespace EmployeeConsole.Models.Mapping
{
    public class EmployeeMap : EntityTypeConfiguration
    {
        public EmployeeMap()
        {
            // Primary Key
            this.HasKey(t => t.empid);

            // Properties
            this.Property(t => t.lastname)
                .IsRequired()
                .HasMaxLength(20);

            this.Property(t => t.firstname)
                .IsRequired()
                .HasMaxLength(10);

            this.Property(t => t.title)
                .IsRequired()
                .HasMaxLength(30);

            this.Property(t => t.titleofcourtesy)
                .IsRequired()
                .HasMaxLength(25);

            this.Property(t => t.address)
                .IsRequired()
                .HasMaxLength(60);

            this.Property(t => t.city)
                .IsRequired()
                .HasMaxLength(15);

            this.Property(t => t.region)
                .HasMaxLength(15);

            this.Property(t => t.postalcode)
                .HasMaxLength(10);

            this.Property(t => t.country)
                .IsRequired()
                .HasMaxLength(15);

            this.Property(t => t.phone)
                .IsRequired()
                .HasMaxLength(24);

            // Table & Column Mappings
            this.ToTable("Employees", "HR");
            this.Property(t => t.empid).HasColumnName("empid");
            this.Property(t => t.lastname).HasColumnName("lastname");
            this.Property(t => t.firstname).HasColumnName("firstname");
            this.Property(t => t.title).HasColumnName("title");
            this.Property(t => t.titleofcourtesy).HasColumnName("titleofcourtesy");
            this.Property(t => t.birthdate).HasColumnName("birthdate");
            this.Property(t => t.hiredate).HasColumnName("hiredate");
            this.Property(t => t.address).HasColumnName("address");
            this.Property(t => t.city).HasColumnName("city");
            this.Property(t => t.region).HasColumnName("region");
            this.Property(t => t.postalcode).HasColumnName("postalcode");
            this.Property(t => t.country).HasColumnName("country");
            this.Property(t => t.phone).HasColumnName("phone");
            this.Property(t => t.mgrid).HasColumnName("mgrid");

            // Relationships
            this.HasOptional(t => t.Employee1)
                .WithMany(t => t.Employees1)
                .HasForeignKey(d => d.mgrid);

        }
    }
}

5. Update App.config to include entity framework config and SQL connection string.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <add name="testContext" connectionString="Data Source=(local);Initial Catalog=test;Integrated Security=True;MultipleActiveResultSets=True"
      providerName="System.Data.SqlClient" />
  </connectionStrings>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>
</configuration>

Utilize your model

The following is a simple program to display a list of employee records by using EmployeeConsole.Models which was defined in testContext.cs.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using EmployeeConsole.Models;

namespace EmployeeConsole
{
    class Program
    {
        static void Main(string[] args)
        {

            using (var db = new testContext())
            {
                // Get all the rows into var query by using LINQ if you want
                //var query = from el in db.Employees orderby el.firstname select el;

                // Get all the rows into var query by using SQL
                var query = db.Employees.SqlQuery("select * from hr.employees");

                // Display Listing Header
                Console.WriteLine("LIST OF EMPLOYEES WITH PHONES:");

                // just display firstnamelastnamephone
                foreach (var item in query)
                {
                    Console.WriteLine("{0}\t{1}\t{2}", item.firstname, item.lastname, item.phone);
                }

                Console.WriteLine("Press any key to exit...");
                Console.ReadKey();
            }
        }
    }
}

Limitation on Processing Raw T-SQL queries

What if when the SQL query changed to the following:

            select * from employees
            select firstname,lastname,phone from hr.employees

Both are valid T-SQL queries, they won’t work from the model generated by Entity Framework because the model mapping has the following:

            this.ToTable("Employees", "HR");
            this.Property(t => t.empid).HasColumnName("empid");

The execution will complain either no schema object ’employees’ in the first case or requiring ’empid’ in the latter.

To use the model generated, it’s better to use either LINQ-TO-ENTITY or ENTITY-SQL. There are differences between Entity SQL and T-SQL.

Further Reading: ADO.NET Entity Framework & Entity SQL

About henry416
I am a computer technology explorer and an university student based on Toronto. If you have any question, please feel free to discuss and comment here

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