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Addamodel-VS.md

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Add a data model in Visual Studio

The following tutorial is based on "Get started with Razor Pages in ASP.NET Core" from docs.microsoft.com.

Prerequisites

Add a data model

In this section, you're adding classes to manage movies in a database.

  1. In Solution Explorer, right-click the RazorPagesMovie project. Select Add > New Folder. Name the folder Models.

  2. Right click the Models folder. Select Add > Class. Name the class Movie.

  3. Replace the contents of the Movie.cs file with the following code:

    namespace RazorPagesMovie.Models;

public class Movie
{
    public int ID { get; set; }
    public string? Title { get; set; }
    public DateTime ReleaseDate { get; set; }
    public string? Genre { get; set; }
    public decimal Price { get; set; }
}

Scaffold the movie model

  1. In Solution Explorer, right click on the Pages folder. Select Add > New Folder.

  2. Name the folder Movies.

  3. In Solution Explorer, right click on the Pages/Movies folder. Select Add > New Scaffolded Item.

  4. In the Add New Scaffolded Item dialog, select Razor Pages on the left pane and select Razor Pages using Entity Framework (CRUD) on the right pane. Then select Add.

  5. Complete the Add Razor Pages using Entity Framework (CRUD) dialog:

    1. In the Model class drop down, select Movie (RazorPagesMovie.Models).
    2. In the Data context class row, select the + (plus) sign.
      1. The Add Data Context dialog opens. Leave the default value and select Add. The class name RazorPagesMovie.Data.RazorPagesMovieContext is generated.
    3. Select Add.

The generated code from the scaffold process creates the following files:

  • Pages/Movies/
    • Create
    • Delete
    • Details
    • Edit
    • Index
  • Data/MovieContext.cs: Class that includes a DbSet property for the entity set. An entity set typically corresponds to a database table, and entity corresponds to a row in the table.

The scaffold process also modifies some existing files:

  • Startup.cs: Created a DB context and registered it with the dependency injection container.
  • appsettings.json: The connection string used to connect to a local database is added.

Use SQLite as the Database

When we scaffolded the database, SqlServer was selected as the default and is a great option for developer ASP.NET Core applications that need a database. For this application let's switch the database use SQLite, small, fast, self-contained, high-reliability, full-featured, SQL database engine. This is easy to do in just a few step:

  1. From the Tools menu, select NuGet Package Manager > Package Manager Console.

  2. Run the following command:

Install-Package Microsoft.EntityFrameworkCore.Sqlite
  1. Update the connection string found in the appsettings.json: Change
"ConnectionStrings": {
    "RazorPagesMovieContext": "Server=(localdb)\\mssqllocaldb;Database=RazorPagesMovieContext-5fff187f-3f2c-4d38-9b74-1812d4621ed3;Trusted_Connection=True;MultipleActiveResultSets=true"
  }

to the following:

  "ConnectionStrings": {
    "RazorPagesMovieContext": "Data Source=MvcMovie.db"
  }
  1. Update the AddDbContext registration in the Program.cs from:
builder.Services.AddDbContext<RazorPagesMovieContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("RazorPagesMovieContext") ?? throw new InvalidOperationException("Connection string 'RazorPagesMovieContext' not found.")));

to the following:

builder.Services.AddDbContext<RazorPagesMovieContext>(options =>
    options.UseSqlite(builder.Configuration.GetConnectionString("RazorPagesMovieContext") ?? throw new InvalidOperationException("Connection string 'RazorPagesMovieContext' not found.")));

Perform initial migration

  1. From the Tools menu, select NuGet Package Manager > Package Manager Console.

  • In the Package Manager Console, enter the following commands:
Add-Migration Initial
Update-Database

Test your app

  1. Press F5 to run your app.

  2. Append /movies to the URL in the browser: http://localhost:port/movies

  3. Create a new entry with the Create link:

    It works!

  4. Test the Edit, Details and Delete links

If you get a SQL exception, verify you have run migrations and updated the database.

Extra light read 7 minutes: If you want to read more on pages you just created click here for more information.

NEXT TUTORIAL: Modifying generated pages