ASP.NET MVC Parent-Child with ViewModel and Entity Framework

This is my code.

Parent:

public class Parent  {      [Key]      public int Id { get; set; }        [Required]      [MaxLength(50), MinLength(3)]      [Display(Name = "Parent Name")]      public string Name { get; set; }        [Required]      [MaxLength(50), MinLength(3)]      [Display(Name = "Parent Surname")]      public string Surname { get; set; }        public List<Child> Children { get; set; } = new List<Child>();  }  

Child:

public class Child  {      [Key]      public int Id { get; set; }        [Required]      [MaxLength(50), MinLength(3)]      [Display(Name = "Child Name")]      public string Name { get; set; }        [Required]      [MaxLength(50), MinLength(3)]      [Display(Name = "Child Surname")]      public string Surname { get; set; }        [Required]      [Display(Name = "Parent")]      public int ParentId { get; set; }        [ForeignKey("ParentId")]      public virtual Parent Parent { get; set; }  }  

ViewModel:

public class ParentChildViewModel  {      public Parent Parent { get; set; }      public IEnumerable<Child> Children { get; set; }  }  

Controller:

public class DemoController : Controller  {      private readonly ApplicationDbContext _db;      public DemoController(ApplicationDbContext db)      {          _db = db;      }      public async Task<IActionResult> Index(int id)      {          var parent = await _db.Parents.AsNoTracking().FirstOrDefaultAsync(i => i.Id == id);            var child = await _db.Children.AsNoTracking().Where(i => i.ParentId == id).ToListAsync();                    var model = new ParentChildViewModel          {              Parent = parent,              Children = child          };            return View(model);      }  }  

View:

@model TwoModels.Models.ParentChildViewModel  <h2> Demo Table Parent</h2>  <table style="border:solid 2px;">      <tr>          <td>              Parent Name:          </td>          <td>              @Html.DisplayFor(m => m.Parent.Name) <br />          </td>      </tr>      <tr>          <td>              Parent Surname:          </td>          <td>              @Html.DisplayFor(m => m.Parent.Surname) <br />          </td>      </tr>  </table>  <h2>Demo Table Child</h2>  <table style="border:solid 2px;">      @foreach (var item in Model.Children)      {          <tr>              <td>                  Child Name:              </td>              <td>                  @Html.DisplayFor(modelItem => item.Name) <br />              </td>          </tr>          <tr>              <td>                  Child Surname:              </td>              <td>                  @Html.DisplayFor(modelItem => item.Surname) <br />              </td>          </tr>      }  </table>  

As is easily understood by the code, I use: _db.Parents.AsNoTracking().FirstOrDefaultAsync(i => i.Id == id) for Parent (I don't want a list, but only First) and: _db.Children.AsNoTracking().Where(i => i.ParentId == id).ToListAsync() (This is a List)

But in this way the request to the database is made twice. So, I would like to modify the code, keeping the use of the ViewModel, but accessing the database only once. I thought of something:

_db.Parents.AsNoTracking().Include(c=>c.Children).Where(i => i.Id == id).ToListAsync();  

How can I change my Controller code and View?

https://stackoverflow.com/questions/65427912/asp-net-mvc-parent-child-with-viewmodel-and-entity-framework December 24, 2020 at 12:49AM