---
title: ASP.NET Core MVC with EF Core - Migrations - 4 of 10
author: tdykstra
description: In this tutorial, you start using the EF Core migrations feature for managing data model changes in an ASP.NET Core MVC application.
manager: wpickett
ms.author: tdykstra
ms.date: 03/15/2018
ms.prod: asp.net-core
ms.technology: aspnet
ms.topic: get-started-article
uid: data/ef-mvc/migrations
---

# ASP.NET Core MVC with EF Core - Migrations - 4 of 10

By [Tom Dykstra](https://github.com/tdykstra) and [Rick Anderson](https://twitter.com/RickAndMSFT)

The Contoso University sample web application demonstrates how to create ASP.NET Core MVC web applications using Entity Framework Core and Visual Studio. For information about the tutorial series, see [the first tutorial in the series](intro.md).

In this tutorial, you start using the EF Core migrations feature for managing data model changes. In later tutorials, you'll add more migrations as you change the data model.

## Introduction to migrations

When you develop a new application, your data model changes frequently, and each time the model changes, it gets out of sync with the database. You started these tutorials by configuring the Entity Framework to create the database if it doesn't exist. Then each time you change the data model -- add, remove, or change entity classes or change your DbContext class -- you can delete the database and EF creates a new one that matches the model, and seeds it with test data.

This method of keeping the database in sync with the data model works well until you deploy the application to production. When the application is running in production it's usually storing data that you want to keep, and you don't want to lose everything each time you make a change such as adding a new column. The EF Core Migrations feature solves this problem by enabling EF to update the database schema instead of creating  a new database.

## Entity Framework Core NuGet packages for migrations

To work with migrations, you can use the **Package Manager Console** (PMC) or the command-line interface (CLI).  These tutorials show how to use CLI commands. Information about the PMC is at [the end of this tutorial](#pmc).

The EF tools for the command-line interface (CLI) are provided in [Microsoft.EntityFrameworkCore.Tools.DotNet](https://www.nuget.org/packages/Microsoft.EntityFrameworkCore.Tools.DotNet). To install this package, add it to the `DotNetCliToolReference` collection in the *.csproj* file, as shown. **Note:** You have to install this package by editing the *.csproj* file; you can't use the `install-package` command or the package manager GUI. You can edit the *.csproj* file by right-clicking the project name in **Solution Explorer** and selecting **Edit ContosoUniversity.csproj**.

[!code-xml[](intro/samples/cu/ContosoUniversity.csproj?range=12-15&highlight=2)]
  
(The version numbers in this example were current when the tutorial was written.) 

## Change the connection string

In the *appsettings.json* file, change the name of the database in the connection string to ContosoUniversity2 or some other name that you haven't used on the computer you're using.

[!code-json[](intro/samples/cu/appsettings2.json?range=1-4)]

This change sets up the project so that the first migration will create a new database. This isn't required to get started with migrations, but you'll see later why it's a good idea.

> [!NOTE]
> As an alternative to changing the database name, you can delete the database. Use **SQL Server Object Explorer** (SSOX) or the `database drop` CLI command:
> ```console
> dotnet ef database drop
> ```
> The following section explains how to run CLI commands.

## Create an initial migration

Save your changes and build the project. Then open a command window and navigate to the project folder. Here's a quick way to do that:

* In **Solution Explorer**, right-click the project and choose **Open in File Explorer** from the context menu.

  ![Open in File Explorer menu item](migrations/_static/open-in-file-explorer.png)

* Enter "cmd" in the address bar and press Enter.

  ![Open command window](migrations/_static/open-command-window.png)

Enter the following command in the command window:

```console
dotnet ef migrations add InitialCreate
```

You see output like the following in the command window:

```console
info: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[0]
      User profile is available. Using 'C:\Users\username\AppData\Local\ASP.NET\DataProtection-Keys' as key repository and Windows DPAPI to encrypt keys at rest.
info: Microsoft.EntityFrameworkCore.Infrastructure[100403]
      Entity Framework Core 2.0.0-rtm-26452 initialized 'SchoolContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
Done. To undo this action, use 'ef migrations remove'
```

> [!NOTE]
> If you see an error message *No executable found matching command "dotnet-ef"*, see [this blog post](http://thedatafarm.com/data-access/no-executable-found-matching-command-dotnet-ef/) for help troubleshooting.

If you see an error message "*cannot access the file ... ContosoUniversity.dll because it is being used by another process.*", find the IIS Express icon in the Windows System Tray, and right-click it, then click **ContosoUniversity > Stop Site**.

## Examine the Up and Down methods

When you executed the `migrations add` command, EF generated the code that will create the database from scratch. This code is in the *Migrations* folder, in the file named *\<timestamp>_InitialCreate.cs*. The `Up` method of the `InitialCreate` class creates the database tables that correspond to the data model entity sets, and the `Down` method deletes them, as shown in the following example.

[!code-csharp[](intro/samples/cu/Migrations/20170215220724_InitialCreate.cs?range=92-118)]

Migrations calls the `Up` method to implement the data model changes for a migration. When you enter a command to roll back the update, Migrations calls the `Down` method.

This code is for the initial migration that was created when you entered the `migrations add InitialCreate` command. The migration name parameter ("InitialCreate" in the example) is used for the file name and can be whatever you want. It's best to choose a word or phrase that summarizes what is being done in the migration. For example, you might name a later migration "AddDepartmentTable".

If you created the initial migration when the database already exists, the database creation code is generated but it doesn't have to run because the database already matches the data model. When you deploy the app to another environment where the database doesn't exist yet, this code will run to create your database, so it's a good idea to test it first. That's why you changed the name of the database in the connection string earlier -- so that migrations can create a new one from scratch.

## The data model snapshot

Migrations creates a *snapshot* of the current database schema in *Migrations/SchoolContextModelSnapshot.cs*. When you add a migration, EF determines what changed by comparing the data model to the snapshot file.

When deleting a migration, use the [dotnet ef migrations remove](https://docs.microsoft.com/ef/core/miscellaneous/cli/dotnet#dotnet-ef-migrations-remove) command. `dotnet ef migrations remove` deletes the migration and ensures the snapshot is correctly reset.

See [EF Core Migrations in Team Environments](/ef/core/managing-schemas/migrations/teams) for more information about how the snapshot file is used.

## Apply the migration to the database

In the command window, enter the following command to create the database and tables in it.

```console
dotnet ef database update
```

The output from the command is similar to the `migrations add` command, except that you see logs for the SQL commands that set up the database. Most of the logs are omitted in the following sample output. If you prefer not to see this level of detail in log messages, you can change the log level in the *appsettings.Development.json* file. For more information, see [Introduction to logging](xref:fundamentals/logging/index).

```text
info: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[0]
      User profile is available. Using 'C:\Users\username\AppData\Local\ASP.NET\DataProtection-Keys' as key repository and Windows DPAPI to encrypt keys at rest.
info: Microsoft.EntityFrameworkCore.Infrastructure[100403]
      Entity Framework Core 2.0.0-rtm-26452 initialized 'SchoolContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
info: Microsoft.EntityFrameworkCore.Database.Command[200101]
      Executed DbCommand (467ms) [Parameters=[], CommandType='Text', CommandTimeout='60']
      CREATE DATABASE [ContosoUniversity2];
info: Microsoft.EntityFrameworkCore.Database.Command[200101]
      Executed DbCommand (20ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      CREATE TABLE [__EFMigrationsHistory] (
          [MigrationId] nvarchar(150) NOT NULL,
          [ProductVersion] nvarchar(32) NOT NULL,
          CONSTRAINT [PK___EFMigrationsHistory] PRIMARY KEY ([MigrationId])
      );

<logs omitted for brevity>

info: Microsoft.EntityFrameworkCore.Database.Command[200101]
      Executed DbCommand (3ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      INSERT INTO [__EFMigrationsHistory] ([MigrationId], [ProductVersion])
      VALUES (N'20170816151242_InitialCreate', N'2.0.0-rtm-26452');
Done.
```

Use **SQL Server Object Explorer** to inspect the database as you did in the first tutorial.  You'll notice the addition of an __EFMigrationsHistory table that keeps track of which migrations have been applied to the database. View the data in that table and you'll see one row for the first migration. (The last log in the preceding CLI output example shows the INSERT statement that creates this row.)

Run the application to verify that everything still works the same as before.

![Students Index page](migrations/_static/students-index.png)

<a id="pmc"></a>
## Command-line interface (CLI) vs. Package Manager Console (PMC)

The EF tooling for managing migrations is available from .NET Core CLI commands or from PowerShell cmdlets in the Visual Studio **Package Manager Console** (PMC) window. This tutorial shows how to use the CLI, but you can use the PMC if you prefer.

The EF commands for the PMC commands are in the [Microsoft.EntityFrameworkCore.Tools](https://www.nuget.org/packages/Microsoft.EntityFrameworkCore.Tools) package. This package is already included in the [Microsoft.AspNetCore.All](xref:fundamentals/metapackage) metapackage, so you don't have to install it.

**Important:** This isn't the same package as the one you install for the CLI by editing the *.csproj* file. The name of this one ends in `Tools`, unlike the CLI package name which ends in `Tools.DotNet`.

For more information about the CLI commands, see [.NET Core CLI](https://docs.microsoft.com/ef/core/miscellaneous/cli/dotnet). 

For more information about the PMC commands, see [Package Manager Console (Visual Studio)](https://docs.microsoft.com/ef/core/miscellaneous/cli/powershell).

## Summary

In this tutorial, you've seen how to create and apply your first migration. In the next tutorial, you'll begin looking at more advanced topics by expanding the data model. Along the way you'll create and apply additional migrations.

> [!div class="step-by-step"]
> [Previous](sort-filter-page.md)
> [Next](complex-data-model.md)