Add Entity Framework Core to an Existing ASP.NET Core Project

I had a Web API application that I was using to test something that had no database interaction at all that I needed to add database interaction too. Going through my posts I didn’t find a guide to add Entity Framework Core to an existing project, so that is what this post is going to cover. We will be using SQLite for our database.

Project Creation

The project we are starting with is just a new ASP.NET Core Web API created using the .NET CLI using the following command from a command prompt.

dotnet new webapi

This gives us a new Web API with no database interaction and makes sure we are all on the same page for the rest of the post.

Project File Changes

Open the csproj file associated with your project. First, we need to add a package reference to the Entity Framework Core tools.

Before:
<ItemGroup>
  <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.5" />
</ItemGroup>

After:
<ItemGroup>
  <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.5" />
  <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.0.1" PrivateAssets="All" />
</ItemGroup>

Next, we need to add a reference to the Entity Framework Core Tools for the .NET CLI.

Before:
<ItemGroup>
  <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.2" />
</ItemGroup>

After:
<ItemGroup>
  <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.2" />
  <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.1" />
</ItemGroup>

The final change to the project file is only needed if you are using SQLite and it is to keep the database file from showing up in the file list. Add the following and adjust app.db to match your database name.

<ItemGroup>
  <None Update="app.db" CopyToOutputDirectory="PreserveNewest" />
</ItemGroup>

App Settings

Now we need to store the database connection string. Again we are using SQLite in this example so if you are trying to use SQL Server (include LocalDb) your connection string will look much different. This is also a place where you need to replace app.db with the database name you want to use.

Open the appsettings.json file and add a ConnectionStrings section similar to the following.

"ConnectionStrings": {
  "DefaultConnection": "DataSource=app.db"
}

The following is my full settings file after the change just to make sure the context is clear.

{
  "ConnectionStrings": {
    "DefaultConnection": "DataSource=app.db"
  },
  "Logging": {
    "IncludeScopes": false,
    "Debug": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    "Console": {
      "LogLevel": {
        "Default": "Warning"
      }
    }
  }
}

Model and Db Context

If you are a long time reader it will be no surprise that the model we will be using is that of a contact. The following is my full contact model.

public class Contact
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Address { get; set; }
    public string City { get; set; }
    public string Subregion { get; set; }
    public string PostalCode { get; set; }
    public string Phone { get; set; }
    public string Email { get; set; }
}

Now that we have a model we need to add a DBContext.

public class ContactsDbContext : DbContext
{
    public DbSet<Contact> Contacts { get; set; }

    public ContactsDbContext(DbContextOptions<ContactsDbContext> options)
        : base(options)
    {

    }
}

Startup

Now that we have the application settings, model, and context from above open up the Startup class and in the ConfigureServices function add the following code to get the ContactsDbContext into the container.

services.AddDbContext<ContactsDbContext>(options => 
    options.UseSqlite(Configuration.GetConnectionString("DefaultConnection")));

Initial Migration

Now that the project is all set to go let’s add an initial migration that will get the table for our contacts set up. From a command prompt in the project directory run the following command.

dotnet ef migrations add Contacts

This will add a Migrations directory to the project with the code needed to add the contacts table. If you want to go ahead and apply the migration to the database run the following command.

dotnet ef database update

Since we didn’t have a database yet the above command creates one which will show up in the root of our project with a name that matches our application settings since we are using SQLite.

Wrapping Up

Adding Entity Framework Core to a project is pretty easy, but not something I do a lot, so this will serve as a good reminder of the steps. Hope it helps you out as well.

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Also published on Medium.