EF Core 插入多对多 table

Question

我用 Razor Pages 构建了我的用户模型，在创建页面上我想在连接处插入用户角色 table UserRoles。

这是我的模型

[Table("Users")]
public class User
{
    public User()
    {
        IsActivo = true;          
    }

    public int Id { get; set; }

    [Required]
    [Display(Prompt = "Username")]
    public string Username { get; set; }
    [Display(Name = "Último Acesso")]
    public DateTime? DataSessao { get; set; }
    [Display(Name = "Activo")]
    public bool IsActivo { get; set; } 
    public Colaborador Colaborador { get; set; }

    public ICollection<UserRoles> UserRoles { get; set; }
}

这是创建模型

public class CreateModel : PageModel
{
    private readonly HutIS.Models.HutISContext _context;

    public CreateModel(HutISContext context)
    {
        _context = context;
    }

    public IActionResult OnGet()
    {
        DepartamentosOptions = _context.Departamento.Select(d =>
              new SelectListItem
                  {
                       Value = d.Id.ToString(),
                       Text = d.Nome
                  }).ToList();


        RolesOptions = _context.Roles.Select(d =>
                  new SelectListItem
                      {
                         Value = d.Id.ToString(),
                         Text = d.Type
                       }).ToList();

        return Page();
    }

    [BindProperty]
    public User User { get; set; }
    public List<SelectListItem> DepartamentosOptions { get; set; }
    public List<SelectListItem> RolesOptions { get; set; }

    public async Task<IActionResult> OnPostAsync()
    {
        if (!ModelState.IsValid)
        {
            return Page();
        }

        _context.User.Add(User);

        await _context.SaveChangesAsync();

        return RedirectToPage("./Index");
    }
}

在 html

<div class="form-group">
    <label asp-for="User.UserRoles" class="control-label"></label>
    <select asp-for="User.UserRoles" asp-items="Model.RolesOptions" class="form-control form-control-sm">
        <option value="">Selecione um Departamento...</option>
    </select>
    <span asp-validation-for="User.UserRoles" class="text-danger"></span>
</div>

我不太确定我该怎么做，当然我在这里遇到了一个例外，但是如果它是 User 中的一个集合，我该如何绑定 UserRoles？

编辑

我解决了异常问题，它与模型属性有关。现在的问题是在 UserRoles table 上没有插入任何内容，我不太确定这样做的方法是什么，因为与 Departments 不同，User 没有到 UserRoles 的导航属性。

如你所见，关系是正确的

Answer 1

对于<select multiple="multiple" asp-for="User.RoleIds" asp-items="Model.RolesOptions" class="form-control form-control-sm">，它将提交RoleId值而不是Role Object，您需要定义public ICollection<int> UserRoleIds { get; set; }接受RoleIds。

按照以下步骤操作：

用 UserRoleIds

定义一个 ViewModel

public class UserVM
{
    public UserVM()
    {
        IsActivo = true;
    }

    public int Id { get; set; }

    [Required]
    [Display(Prompt = "Username")]
    public string Username { get; set; }
    [Display(Name = "Último Acesso")]
    public DateTime? DataSessao { get; set; }
    [Display(Name = "Activo")]
    public bool IsActivo { get; set; }

    public ICollection<int> RoleIds { get; set; }
}

剃须刀型号

public class CreateModel : PageModel
{
    private readonly TestRazorContext _context;

    public CreateModel(TestRazorContext context)
    {
        _context = context;
    }

    public IActionResult OnGet()
    {
        RolesOptions = _context.Role.Select(d =>
                new SelectListItem
                {
                    Value = d.Id.ToString(),
                    Text = d.Type
                }).ToList();
        return Page();
    }

    [BindProperty]
    public UserVM User { get; set; }
    public List<SelectListItem> RolesOptions { get; set; }

    public async Task<IActionResult> OnPostAsync()
    {
        if (!ModelState.IsValid)
        {
            return Page();
        }
        //create user
        var user = new User {
            Username = User.Username,
            //rest properties
        };
        _context.User.Add(user);
        await _context.SaveChangesAsync();
        //set user role
        var userRoles = new List<UserRoles>();
        foreach (var roleId in User.RoleIds)
        {
            userRoles.Add(new UserRoles
            {
                UserId = user.Id,
                RoleId = roleId
            });
        }
        _context.UserRole.AddRange(userRoles);
        await _context.SaveChangesAsync();
        return RedirectToPage("./Index");
    }
}

Razor 视图

<form method="post">
    <div class="form-group">
        <label asp-for="User.Username" class="control-label"></label>
        <input asp-for="User.Username" />
    </div>    
    <div class="form-group">
        <label asp-for="User.RoleIds" class="control-label"></label>
        <select multiple="multiple" asp-for="User.RoleIds" asp-items="Model.RolesOptions" class="form-control form-control-sm">
            <option value="">Selecione um Departamento...</option>
        </select>
        <span asp-validation-for="User.RoleIds" class="text-danger"></span>
    </div>
    <input type="submit" value="Submit"/>
</form>

EF Core 插入多对多 table

EF Core Insert in many to many table

c#

asp.net-core

razor-pages

ef-core-2.0