Setup

Setting up entity framework core

Using the demo project

In order to save time, we will be starting to learn entity framework by using a project which is built on mvc and currently has:

• a movie model

• a movie controller for crud operations on movie

• cshtml view files for corresponding crud operations

• a fake context class which the controllers use

Get the demo project from repo

GitHub - raviramorg/MvcMovie: For learning ASP.NET CoreGitHub

You need to check out the initial version of this project to get started with the above demo project

Add package reference

Add the required package reference to the Visual Studio solution file.

<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="7.0.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="7.0.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="7.0.0"/>

Add the DbContext class

The context object allows querying and saving data. The database context is derived from Microsoft.EntityFrameworkCore.DbContext and specifies the entities to include in the data model.

Add a class called MvcMovieContext inside the Data folder of the project:

Replace the code inside MvcMovieContext with the below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using MvcMovie.Models;

namespace MvcMovie.Data
{
    public class MvcMovieContext : DbContext
    {
        public MvcMovieContext (DbContextOptions<MvcMovieContext> options)
            : base(options)
        {
        }

        public DbSet<MvcMovie.Models.Movie> Movie { get; set; }
    }
}

Add the data context as a service in program.cs file

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddDbContext<MvcMovieContext>(options =>
       options.UseSqlServer(builder.Configuration.GetConnectionString("MvcMovieContext")));

This will let us perform a Dependency Injection to inject the MvcMovieContext database context into any controller later. We will discuss dependency injection little later.

Add connection string

Let us add a connection string in appsettings.json file so that the application knows which database to connect to. In our case we will be using local DB which is a sequel server instance for developers. Local DB is installed automatically when we install Visual Studio.

appsettings.json file

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "MvcMovieContext": "Data Source = (localdb)\\MSSQLLocalDB;Initial Catalog=MvcMovie;Integrated Security=True;"
  }
}

Creating the database

Entity framework is capable of creating database and tables by what is called as migrations which we will look into later. To keep the demo simple, let us manually create the required database, table and the data using the query below:

use master;  
go 
create database MvcMovie; 
go
use MvcMovie;
go

CREATE TABLE [dbo].[Movie] (
[Id]          INT             IDENTITY (1, 1) NOT NULL,
[Title]       NVARCHAR (MAX)  NULL,
[ReleaseDate] DATETIME2 (7)   NOT NULL,
[Genre]       NVARCHAR (MAX)  NULL,
[Price]       DECIMAL (18, 2) NOT NULL
);

insert into Movie values ('Titanic', '1/1/1997','Romance',99);
insert into Movie values ('Jurassic Park', '12/25/1993','Fiction',199);

Next, we will look into how to use the context object in the controller, instead of the fake context object that the application is currently using.