Code First migration in asp.net MVC 4

Introduction: In this article I will explain how we can enable Code First migration in asp.net MVC 4

Description:

In the previous article I have explained Create, Read, Update and Delete in Asp.net with MVC 4 Razor view Engine using Entity framework with Code first approach, How to integrate Captcha in asp.net,What is Scaffolding in Asp.net MVC?, How to create Contact Us page in Asp.net and What is Asp.net MVC? Its advantages and disadvantges.

Migration is used to backup our database when we are going to develop application using code first approach in asp.net MVC.

I have a class named Student_Detail.cs in Models:

public class Student_Detail

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public string Subject { get; set; }

        public int Marks { get; set; }

    } 

Now I add a new property in this class for student address.

public class Student_Detail

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public string Subject { get; set; }

        public int Marks { get; set; }

        public string Address { get; set; }

    } 

Build the project and run the application. You got an Exception:

“The model backing the 'ProjectContext' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269).”

See attached snapshot:

                                                                                         (Click to enlarge)

If you see exception/error carefully it suggests the solution:

Use Code First Migrations to update the database

Step 1: To update database using Code first Migration go to Tools>>Library Package Manager >> Package Manager Console as shown in snapshot:

                                                                                               (Click to enlarge)

Package Manager Console will be open and type the given command:

enable-migrations

Hit the enter button. It will show output of all context you have in project. Copy the context for that you want to enable migration. Here I run the following command:

PM> Enable-Migrations -ContextTypeName MVCAPPLICATION.Models.ProjectContext

As command execute it will show you enabled message for context as show in attached snapshot:

                                                                                             (Click to enlarge)

It will create Migration folder in project with configuration.cs (seed method) and InitialCreate target migration (up and down methods) see attached snapshot:

                                                                                            (Click to enlarge)

Step 2: After that in configuration.cs file change the AutomaticMigrationsEnabled to true:

public Configuration()

        {

            AutomaticMigrationsEnabled = true;

        }

Step 3: open Global.asax file and add the namespace:

using MVCAPPLICATION.Models;

using System.Data.Entity;

Add the given code to Application_Start in Global.asax file:

Database.SetInitializer<ProjectContext>(null);

Step 4: Run the command in Package Manager Console:

update-database

Now you see a column has been added to table in database. Add the column in views files or add a new Controller. Run the application and see the result.

I hope this article helps you to use code first Migration to update the database.

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