Get Confused and Excited with Running Migrations in Visual Studio
What Even is a Migration?
Are you lost in a sea of code changes and a database schema that just won’t keep up? Fear not, dear developer, for migrations are here to help! Migrations are simply a set of instructions to update your database schema as you make changes to your models. They automate this tedious process and ensure that your code and database are always in sync.
Getting Started with Migrations
First things first, in the .NET world, Entity Framework Migrations is the tool of choice. But how do you even set up your project for migrations? It’s simpler than you think!
Step 1: Install Entity Framework Migrations
If you haven’t already, use the NuGet Package Manager in Visual Studio to install Entity Framework Migrations.
Step 2: Create a Migration Configuration
Now, navigate to your project in the Solution Explorer, right-click and select “Add > New Item…”. Choose “ADO.NET Entity Data Model” and give it a name. This creates a new model file with a .edmx extension. Once it’s created, right-click it in the Solution Explorer and select “Add Code Generation Item…”. Choose “EF 6.x EntityObject Generator” and give it a name. This creates a new T4 template file with a .tt extension. Open this file and add the following code at the top:
<#@ template language="C#" hostspecific="True" #> <#@ output extension=".cs" #> <#@ parameter name="ContextNamespace" type="System.String" #> <#@ parameter name="ContextName" type="System.String" #> <#@ parameter name="ModelNamespace" type="System.String" #>
This code sets up the T4 template to generate Entity Framework code for your model and context.
Step 3: Enable Migrations
Now that you have set up your project for migrations, enable them by opening the Package Manager Console (View > Other Windows > Package Manager Console) and running the following command:
Enable-Migrations -ProjectName [YourProjectName] -StartUpProjectName [YourProjectName]
Replace [YourProjectName] with the name of your project. This command creates a Configuration.cs file in your project for managing migrations.
Creating and Running a Migration
Now that you’ve successfully set up your project for migrations, let’s create and run one!
Step 1: Add a New Migration
To create a new migration, open the Package Manager Console and run the following command:
Add-Migration [MigrationName] -ProjectName [YourProjectName] -StartUpProjectName [YourProjectName]
Replace [MigrationName] with a descriptive name for your migration. This command creates a new migration file in your project containing the changes to your database schema.
Step 2: Modify the Migration
The migration file has a series of instructions that describe changes to your database schema. Add or remove instructions as you see fit.
Step 3: Update the Database
To update the database with the changes from your migration, open the Package Manager Console and run the following command:
Update-Database -ProjectName [YourProjectName] -StartUpProjectName [YourProjectName]
This applies the changes from your migration to the database.
Step 4: View the Migration History
You can view the migration history by opening the Configuration.cs file in your project, which displays all the applied migrations.
Migrations keep your database schema and code in sync, and with Entity Framework Migrations in Visual Studio, running them couldn’t be easier! Follow these steps to set up and use migrations in your development workflow with ease.