实体框架一对多关系代码首先是asp .net mvc 5和jquery autocomplete

Question

I want to create a simple website where user can add offerts with some details like title, description, city, time.

This is a part of my database diagram.

1. User can create many offerts
2. City can have many offerts
3. Region can have many cities.

City table

public class City
{
    public int CityID { get; set; }

    [StringLength(50, MinimumLength = 2)]
    public string Name { get; set; }

    public int RegionID { get; set; }
    public virtual Region Region { get; set; }

    public virtual ICollection<Offert> Offerts { get; set; }        
}

Region table

public class Region
{
    public int RegionID { get; set; }

    [StringLength(30, MinimumLength=3)]
    public string Name { get; set; }

    public virtual ICollection<City> Cities { get; set; }
}

Offert table:

public class Offert
{
    // Properties
    public int OffertID { get; set; }

    [Required]
    [MaxLength(30)]
    [Display(Name = "Title", ResourceType = typeof(Resource))]
    public string Title { get; set; }

    [Required]
    [DataType(DataType.MultilineText)]
    [Display(Name = "Description", ResourceType = typeof(Resource))]
    [StringLength(100, ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "Bad_Description", MinimumLength = 6)]
    public string Description { get; set; }

    [Required]
    [DataType(DataType.DateTime)]
    [Display(Name = "When", ResourceType = typeof(Resource))]
    public DateTime When { get; set; }

    // Relationships
    public int CityID { get; set; }
    [Display(Name = "City", ResourceType = typeof(Resource))]
    public virtual City City { get; set;

    public virtual ApplicationUser User { get; set; }
}

User table:

 public class ApplicationUser : IdentityUser
{       
    public virtual ICollection<Offert> Offerts { get; set; }
    public virtual MyUserInfo MyUserInfo { get; set; }

    public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
    {
        var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
        return userIdentity;
    }
}

Relationships are are created using fluent api:

 public class Pako_Context : IdentityDbContext<ApplicationUser>
{
    public Pako_Context()
        : base("database_context")
    {
        this.Configuration.LazyLoadingEnabled = false;
        this.Configuration.ProxyCreationEnabled = false;
    }

    public static Pako_Context Create()
    {
        return new Pako_Context();
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<ApplicationUser>()
            .HasMany(user => user.Offerts)
            .WithRequired();

        modelBuilder.Entity<Region>()
            .HasMany(c => c.Cities)
            .WithRequired(r => r.Region);

        modelBuilder.Entity<City>()
            .HasMany(o => o.Offerts)
            .WithRequired(c => c.City);
    }

    public DbSet<City> Cities { get; set; }
    public DbSet<Region> Regions { get; set; }
    public DbSet<Offert> Offerts { get; set; }
    public DbSet<MyUserInfo> MyUserInfo { get; set; }
}

I have 2 problems:

1. How to pass data from view to controller? Currently jquery autocomplete mechanism returns string which contains city name, but this value is not visible inside controller.

Offert create view:

    <div class="form-group">
        @Html.LabelFor(model => model.City.Name, "City", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.City.Name, new { htmlAttributes = new { @class = "form-control", @id = "autocomplete", data_autocomplete_url = Url.Action("Autocomplete") } })

            @Html.ValidationMessageFor(model => model.City.Name, "", new { @class = "text-danger" })
        </div>
    </div> 

2. Currently as workaround of problem number 1, I just pick up some random city from database and add this to my offert.

Offert controller create method:

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create([Bind(Include = "OffertID,Title,Description,When,City.Name")] Offert offert)
    {
        if (ModelState.IsValid)
        {
            string currentUserId = User.Identity.GetUserId();
            ApplicationUser currentUser = db.Users.FirstOrDefault(x => x.Id == currentUserId);
            offert.User = currentUser;
            City RandomCity = db.Cities.FirstOrDefault();
            offert.City = RandomCity;
            db.Offerts.Add(offert);
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(offert);
    }

But when I invoke db.SaveChanges(); Method following exception occur:

Additional information: Entities in 'Pako_Context.Offerts' participate in the 'ApplicationUser_Offerts' relationship. 0 related 'ApplicationUser_Offerts_Source' were found. 1 'ApplicationUser_Offerts_Source' is expected.

I tried to add offert record to ApplicationUser but it didn't work. Probably I don't understand this message correctly. How to resolve problems 1 and 2?

Answer 1

For your first issue, you have to change the autocomplete and make it through JavaScript in order to pick the selected value from the user, then updae this value in a Hidden Field. You have to make this hidden field with the name CityID

        @Html.HiddenFor(model => model.CityID)

If you are using Autocomplete plugin, then it should be like this:

$("#City_Name").autocomplete({ source: "PUT the source here for your Cities", minLength: 2, select: function (event, ui) { $("#CityID").val(ui.item.id); } })

As for the second issue, it says that you have a relation between User and Offers and this relation is required, so you have to have at least one offer in the Offers collection, so try to add this line:

currentUser.Offerts.Add(offert);