如何从数据库中填充 ASP.NET 实体框架中的列表

Question

我正在尝试制作可以管理客户的应用程序。我所有的客户都有他自己的客户，由我管理。所以我为我的客户创建了两个表tboClienti 和tboSottoClienti 为我的“下客户”创建了数据库。

这是表格的结构：

Structure of table Clients - tboClienti 和 structure of table Under Clients - tboSottoClienti。

我正在为我的“下属客户”进行 CRUD 操作，我想制作下拉列表，我可以在其中选择我的客户并为我的下属客户插入信息（姓名、姓氏、公司、电话）。

This is how I imagine it.

我为我的下客户端制作了一个控制器模型和视图，但我不知道如何在我的 View Razor 页面中制作列表。

这是控制器：

public class SottoClientiController : Controller
{
    private readonly AppDbContext _db;

    public SottoClientiController(AppDbContext db)
    {
        _db = db;
    }

    public IActionResult Index()
    {
        var datiSottoClienti = _db.tboSottoClienti.ToList();
        return View(datiSottoClienti);
    }


    public IActionResult CreareLista()
    {
        ViewData["lstClieti"] = new SelectList(_db.tboClienti, "Id", "Nome_azienda");
        return View();
    }
    public IActionResult CreareSottoCliente()
    {
        return View();
    }

    [HttpPost]
    public async Task<IActionResult> CreareSottoCliente(SottoCliente sottoCliente) 
    {
        if (ModelState.IsValid)
        {
            _db.Add(sottoCliente);
            await _db.SaveChangesAsync();
            return RedirectToAction("Index");
        }

        return View(sottoCliente);
    }
}

这是模型类：

public class SottoCliente
{
    [Key]
    public int Id { get; set; }

    [Required(ErrorMessage = "Inserisci il nome di proprietario dell'azienda")]
    [Display(Name = "Nome")]
    public string Nome { get; set; }

    [Required(ErrorMessage = "Inserisci il cognome di proprietario dell'azienda")]
    [Display(Name = "Cognome")]
    public string Cognome { get; set; }

    [Display(Name = "Azienda")]
    public string Azienda { get; set; }

    [Required(ErrorMessage = "Inserisci il numero di telefono dell'azienda")]
    [DataType(DataType.PhoneNumber)]
    [Display(Name = "Telefono")]
    [RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$",
       ErrorMessage = "Numero non valido")]
    public string Cellulare { get; set; }
}

我不知道如何从表tboClienti 中获取数据以将其插入列表。所以这样我就可以为我的下属客户选择客户。

这是视图：

<h4>Under Client</h4>
<hr />
<div class="row">
    <div class="col-md-4">
        <form asp-action="CreareSottoCliente">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>

           <div class="form-group">
            <label asp-for="Azienda" class="control-label"></label>
            <select asp-for="Azienda" class="form-control" asp-items="@ViewBag.lstClieti"></select>
            <span asp-validation-for="Azienda" class="text-danger"></span>
        </div>

            <div class="form-group">
                <label asp-for="Id" class="control-label"></label>
                <input asp-for="Id" class="form-control" />
                <span asp-validation-for="Id" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Nome" class="control-label"></label>
                <input asp-for="Nome" class="form-control" />
                <span asp-validation-for="Nome" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Cognome" class="control-label"></label>
                <input asp-for="Cognome" class="form-control" />
                <span asp-validation-for="Cognome" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Azienda" class="control-label"></label>
                <input asp-for="Azienda" class="form-control" />
                <span asp-validation-for="Azienda" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Cellulare" class="control-label"></label>
                <input asp-for="Cellulare" class="form-control" />
                <span asp-validation-for="Cellulare" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-primary" />
            </div>
        </form>
    </div>
</div> 

我将连接字符串插入appsettings.json，然后将其添加到ConfigureServices();。

这是数据库上下文的类：

 public class AppDbContext: DbContext
 {
        public AppDbContext(DbContextOptions<AppDbContext> options): base (options)
        {
        }

        public DbSet<Tecnico> tboTecnici { get; set; }
        public DbSet<Cliente> tboClienti { get; set; }
        public DbSet<SottoCliente> tboSottoClienti { get; set; }
}

对如何从数据库中获取数据并将其插入列表有什么建议吗？

提前致谢！

Answer 1

在 ASP.NET Core MVC 中，下拉列表的 HTML 代码如下所示

 <div class="form-group">
        <label asp-for="NewsTypeId" class="control-label"></label>
        <select asp-for="NewsTypeId" class="form-control" asp-items="@ViewBag.NewsTypeId"></select>
        <span asp-validation-for="NewsTypeId" class="text-danger"></span>
    </div>

在 C# 控制器中

public IActionResult Create()
{
    ViewData["NewsTypeId"] = new SelectList(_context.TypeOfNews, "TypeId", "TypeName");
    return View();
}

原答案：https://stackoverflow.com/a/55843644/3559462

有关更详细的分步程序，请查看此链接：https://www.c-sharpcorner.com/article/binding-dropdown-list-with-database-in-asp-net-core-mvc/

Answer 2

调试您的代码并确保您的 ViewData["lstClieti"] 确实存在值。

确定您的视图名称是否为CreareLista。如果视图名称为CreareSottoCliente。 如下更改：

//public IActionResult CreareLista()
//{
//    ViewData["lstClieti"] = new SelectList(_db.tboClienti, "Id", "Nome_azienda");
//    return View();
//}
public IActionResult CreareSottoCliente()
{
    ViewData["lstClieti"] = new SelectList(_db.tboClienti, "Id", "Nome_azienda");
    return View();
}

整个演示：

1.型号：

public class SottoCliente
{
    [Key]
    public int Id { get; set; }

    [Required(ErrorMessage = "Inserisci il nome di proprietario dell'azienda")]
    [Display(Name = "Nome")]
    public string Nome { get; set; }

    [Required(ErrorMessage = "Inserisci il cognome di proprietario dell'azienda")]
    [Display(Name = "Cognome")]
    public string Cognome { get; set; }

    [Display(Name = "Azienda")]
    public string Azienda { get; set; }

    [Required(ErrorMessage = "Inserisci il numero di telefono dell'azienda")]
    [DataType(DataType.PhoneNumber)]
    [Display(Name = "Telefono")]
    [RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$",
       ErrorMessage = "Numero non valido")]
    public string Cellulare { get; set; }
}
public class Cliente
{
    public int Id { get; set; }
    public string Nome_azienda { get; set; }
}

2.视图名称应为CreareSottoCliente.cshtml。

3.控制器：

public class SottoClientiController : Controller
{
    private readonly MvcProj3_1Context _db;
    public SottoClientiController(MvcProj3_1Context db)
    {
        _db = db;
    }

    public IActionResult Index()
    {
        var datiSottoClienti = _db.tboSottoClienti.ToList();
        return View(datiSottoClienti);
    }
    //SottoClienti/CreareSottoCliente
    public IActionResult CreareSottoCliente()
    {
        ViewData["lstClieti"] = new SelectList(_db.tboClienti, "Id", "Nome_azienda");
        return View();
    }

    [HttpPost]
    public async Task<IActionResult> CreareSottoCliente(SottoCliente sottoCliente)
    {
        if (ModelState.IsValid)
        {
            _db.Add(sottoCliente);
            await _db.SaveChangesAsync();
            return RedirectToAction("Index");
        }

        return View(sottoCliente);
    }
}

4.DbContext：

public class MvcProj3_1Context : DbContext
{
    public MvcProj3_1Context (DbContextOptions<MvcProj3_1Context> options)
        : base(options)
    {
    }       
    public DbSet<Tecnico> tboTecnici { get; set; }
    public DbSet<Cliente> tboClienti { get; set; }
    public DbSet<SottoCliente> tboSottoClienti { get; set; }
}

5.Startup.cs：

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllersWithViews();

    services.AddDbContext<MvcProj3_1Context>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("MvcProj3_1Context")));
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseHttpsRedirection();
    app.UseStaticFiles();

    app.UseRouting();

    app.UseAuthorization();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute(
            name: "default",
            pattern: "{controller=Home}/{action=Index}/{id?}");
    });
}

6.appSettings.json：

"ConnectionStrings": {
   "MvcProj3_1Context": "Server=(localdb)\\mssqllocaldb;Database=DatabaseName;Trusted_Connection=True;MultipleActiveResultSets=true"
}

结果：