EF Code First Migrations database migration, efmigrations

EF Code First Migrations database migration, efmigrations
1. EF Code First creates a database

Step 1: Create a console application

Step 2: Install EntityFramework

Run the following statement on the Package Manager Console:

PM> Install-Package EntityFramework

2. Project Structure

Two entities and ing. The PortalContext code is as follows:

using System;using System.Collections.Generic;using System.Data.Common;using System.Data.Entity;using System.Linq;using System.Text;using System.Threading.Tasks;using Portal.Enities;using Portal.Mapping;namespace Portal{    public class PortalContext : DbContext    {        static PortalContext()        {            System.Data.Entity.Database.SetInitializer<PortalContext>(null);           //Database.SetInitializer(new DropCreateDatabaseAlways<PortalContext>());        }        public DbSet<Category> Categories { get; set; }        public DbSet<Province> Provinces { get; set; }        /// <summary>        /// This method is called when the model for a derived context has been initialized, but        /// before the model has been locked down and used to initialize the context.  The default        /// implementation of this method does nothing, but it can be overridden in a derived class        /// such that the model can be further configured before it is locked down.        /// </summary>        /// <remarks>        /// Typically, this method is called only once when the first instance of a derived context        /// is created.  The model for that context is then cached and is for all further instances of        /// the context in the app domain.  This caching can be disabled by setting the ModelCaching        /// property on the given ModelBuidler, but note that this can seriously degrade performance.        /// More control over caching is provided through use of the DbModelBuilder and DbContextFactory        /// classes directly.        /// </remarks>        /// <param name="modelBuilder"> The builder that defines the model for the context being created. </param>        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            modelBuilder.Configurations.Add(new CategoryMap());            modelBuilder.Configurations.Add(new ProvinceMap());        }    }}

Other codes can be downloaded from the end of this blog.

3. EF Code First database migration

Step 1: generate a database

Modify the static constructor of PortailContext. cs to cancel the settings of the current database reconstruction database when the database model changes.

static PortalContext()        {            System.Data.Entity.Database.SetInitializer<PortalContext>(null);            //Database.SetInitializer(new DropCreateDatabaseAlways<PortalContext>());        }

Step 2: On the Package Manager Console, execute the following statement:

PM> Enable-Migrations-EnableAutomaticMigrations

The running result is as follows:

The Configuration code is as follows:

namespace Portal.Migrations{    using System;    using System.Data.Entity;    using System.Data.Entity.Migrations;    using System.Linq;    internal sealed class Configuration : DbMigrationsConfiguration<Portal.PortalContext>    {        public Configuration()        {            AutomaticMigrationsEnabled = true;        }        protected override void Seed(Portal.PortalContext context)        {            //  This method will be called after migrating to the latest version.            //  You can use the DbSet<T>.AddOrUpdate() helper extension method             //  to avoid creating duplicate seed data. E.g.            //            //    context.People.AddOrUpdate(            //      p => p.FullName,            //      new Person { FullName = "Andrew Peters" },            //      new Person { FullName = "Brice Lambson" },            //      new Person { FullName = "Rowan Miller" }            //    );            //        }    }}

Step 3: run the following statement on the Package Manager Console:

PM> Add-Migration InitialCreate

The running result is as follows:

Step 4: run the following statement on the Package Manager Console:

PM> Update-Database-Verbose

The execution result is as follows:

At this point, the data has been created:

4. EF Code First adds an object

Step 1: add the City. cs entity

Step 2: run the following statement on the Package Manager Console:

PM> Add-Migration AddCity

The execution result is as follows:

Step 3: update the object to the database and execute the following statement on the Package Manager Console

PM> Update-Database-Verbose

Database changes are as follows:

5. EF Code First modifies an object

Step 1: Modify the City and add the CityNo attribute

Step 2: run the following code in the Package Manager Console:

PM> Add-Migration UpdateCity

The execution result is as follows:

Step 3: run the following statement on the Package Manager Console:

PM> Update-Database-Verbose

The execution result is as follows:

6. Version Tracing

Step 1: Modify the City in the database and delete the CityNo Field

Step 2: run the following statement on the package manager controller:

PM> Add-Migration ModifyCity

Step 3: update to the database and run the following statement on the Package Manager Console:

PM> Update-Database-Verbose

Run the following statement on the Package Manager Console:

PM> Update-Database-SourceMigration "201701_1349455_addcity.cs"

The execution result is as follows:

7. Other commands

1. enable database migration for the specified DbContext

PM> Enable-Migrations -ContextTypeName Portal.PortalContext

2. Set whether automatic migration is allowed

Enable-Migrations

Constructor of the generated Configuration. cs File

public Configuration(){      AutomaticMigrationsEnabled = false;}

3. Enable-Migrations specifies the project name

PM>Enable-Migrations -StartUpProjectName Portal

If the default project is selected in the "Package Manager Console", you can not set the "-StartUpProjectName" parameter. If you execute this command multiple times, you can add the-Force parameter.

4. view the executed SQL statement-Verbose command

Update-Database -Verbose 

8. Sample download

Portal sample download: http://files.cnblogs.com/files/zsy/Portal.rar