iimamul / entityframeworkdemogs1

EntityFrameworkDemoGS1

• First install or update entity framework CLI from here. EF Core tools reference (.NET CLI) - EF Core | Microsoft Learn
• Now create webapi project in VS.
• Install two nuget packages from package manager
  • EntityFrameworkCore.SqlServer
  • If you are using Visual Studio then: EntityFrameworkCore.Tools
  • If using VS Code or other text editor then: EntityFrameworkCore.Design
• Now create ApplicationDbContext class and inherit from DbContext. Then hit ctrl+. to first add the using statement, then again hit same buttons for implement constructor from popup options.
• Now we need to add SQL server connection string into appsettings.development.json then add it into Program.cs** with builder services appsettings.development.json

  "ConnectionStrings": {
    "DefaultConnection": "Server=localhost,1433;Database=EFCoreDemoGS1;User Id=sa;Password=sql@123;TrustServerCertificate=True;"
  }

Program.cs

builder.Services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"))
    );

• Now create a Genre.cs class with Id and Name property, and add DbSet Property into ApplicationDbContext.cs class.
• Now add migration, if you are in vs code or Visual studio then command will be different for both. For Visual Studio

Add-Migration Initial
Update-Database

For VS Code

dotnet ef migrations add Initial
dotnet ef database update

• In entity framework core, there are three-way to making configuration (Means, 3 way to tell EF about DB table configuration). Out of 3, fluent API one is most power one because it has maximum options.

  • By Convention, like Id attribute will be set as the primary key of the table
  • By Data Annotation, like [Key] is telling db that below's attribute is the db key or primary key.
  • By fluent API in the ApplicationDbContext.

     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);
     
         modelBuilder.Entity<Genre>().HasKey(k=> k.Id);
     }

• Set convention for all string in Program.cs

   protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
   {
       configurationBuilder.Properties<string>().HaveMaxLength(150);
   }

• If we need to change this for specific property then we can just add it OnModelCreating method.

   modelBuilder.Entity<Comment>().Property(c => c.Content).HasMaxLength(500);

• These configurations inside OnModelCreating can grow very long so we'll shift them into separate config file inside Entities>Configurations

• In every config file, implement IEntityTypeConfiguration interface with their individual type.

• After separating all the configuration, add this line inside OnModelCreating

   modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());

• Now we'll add relation between our entities, like below. We added MovieId and Movie navigation property in comment to establish relation between them.

       public class Comment
       {
           public int Id { get; set; }
           public string? Content { get; set; }
           public bool Recommend { get; set; }
           public int MovieId { get; set; }
           public Movie Movie { get; set; } = null!;
       }

Ignore circular reference error of json serializer

• Change this line in Program.cs

//change this into belows code
//builder.Services.AddControllers();
builder.Services.AddControllers()
    .AddJsonOptions(options => options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles);

Connected and disconnected model update

    //connected model because genre first loaded by context and same model will be updated
    [HttpPut("{id:int}/update")]
    public async Task<ActionResult<Actor>> Put(int id)
    {
        var genre = await context.Genres.FirstOrDefaultAsync(a => a.Id == id);

        if (genre is null)
        {
            return NotFound();
        }
        genre.Name += "2";
        await context.SaveChangesAsync();
        return Ok(genre);
    }

    //disconnected model because genre not loaded from context model
    [HttpPut("{id:int}/update2")]
    public async Task<ActionResult<Actor>> Put(int id, GenreCreationDTO genreDto)
    {
        var genre = mapper.Map<Genre>(genreDto);

        genre.Id = id;
        context.Update(genre);
        await context.SaveChangesAsync();
        return Ok(genre);
    }

Delete in two ways

    [HttpDelete("{id:int}/newway")]
    public async Task<ActionResult> Delete(int id)
    {
        var deletedRows = await context.Genres.Where(g => g.Id == id).ExecuteDeleteAsync();
        if (deletedRows == 0)
        {
            return NotFound();
        }

        return NoContent();
    }

    [HttpDelete("{id:int}/oldway")]
    public async Task<ActionResult> DeleteOldWay(int id)
    {
        var genre = await context.Genres.FirstOrDefaultAsync(g => g.Id == id);
        if (genre is null)
        {
            return NotFound();
        }

        context.Remove(genre);
        await context.SaveChangesAsync();

        return NoContent();
    }

link