asp.net-mvc - MVC模型验证

Question

因此，我目前正在构建需要验证用户模型的应用程序，如果用户填写了不正确的属性，它将告诉他们。
我已经设置了数据注释，但是我不确定如何将错误消息转发回用户？
到目前为止，我已经在模型和 View 上进行了设置。

模型

public class DatabaseModel
    {
        [Required(ErrorMessage = ("A first name is required"))]
        public string FirstName { get; set; }
        [Required(ErrorMessage = ("A last name is required"))]
        public string LastName { get; set; }
        [Required(ErrorMessage = ("A valid role is required"))]
        public string Role { get; set; }
        // TODO - Validate rank to only b 1 - 10
        //
        [Range(1,10, ErrorMessage = ("A rank between 1 and 10 is required"))]
        public int Rank { get; set; }      

    }

和 View

@model RoleCreatorAndEditor.Models.DatabaseModel
@{
    ViewData["Title"] = "Index";
}

<h2>User Information</h2>

<p>This is your user information!</p>

@using (Html.BeginForm("Index", "Home", FormMethod.Post)) {
    @Html.Label("First Name")
    <br>
    @Html.TextBoxFor(m => m.FirstName)
    <br>
    @Html.Label("Last Name")
    <br>
    @Html.TextBoxFor(m=>m.LastName)
    <br>
    @Html.Label("Role")
    <br>
    @Html.TextBoxFor(m => m.Role)
    <br>
    @Html.Label("Rank")
    <br>
    @Html.TextBoxFor(m => m.Rank)
    <br><br>
    <input type="submit" value="Save">
}

我的 Controller

public class HomeController : Controller
    {
        // GET: Home
        [HttpGet]
        public ActionResult Index()
        {
            DatabaseModel model = new DatabaseModel();
            return View(model);
        }
        [HttpPost]
        public ActionResult Index(DatabaseModel model)
        {
            if (ModelState.IsValid)
            {
                ListToDatatable convert = new ListToDatatable();
                DataTable user = convert.Convert(model);
                DatabaseRepository dbRepo = new DatabaseRepository();
                dbRepo.Upload(user);
            }
            return View();
        }
    }

我认为需要将模型传递回 View 以显示错误消息，尽管我已阅读过asp.net上的文档，但我无法理解他们是如何添加错误消息的，并且表单知道如何显示错误消息。给用户的错误。

我非常困惑。

Answer 1

您需要在Controller中使用ModelState.IsValid，并在 View 中使用@Html.ValidationMessageFor(model => model.FirstName):

public ActionResult Index(ViewModel _Model) 
{ 
    // Checking whether the Form posted is valid one. 
    if(ModelState.IsValid) 
    { 
        // your model is valid here.
        // perform any actions you need to, like database actions,
        // and/or redirecting to other controllers and actions.
    }
    else 
    {
        // redirect to same action
        return View(_Model);
    } 
}

例如:

@model RoleCreatorAndEditor.Models.DatabaseModel
@{
    ViewData["Title"] = "Index";
}

<h2>User Information</h2>

<p>This is your user information!</p>
@using (Html.BeginForm("Index", "Home", FormMethod.Post)) {
    @Html.LabelFor(m=>m.FirstName)
    <br>
    @Html.TextBoxFor(m => m.FirstName)
    @Html.ValidationMessageFor(model => model.FirstName, "", new { @class = "text-danger" })

    <br>
    @Html.LabelFor(m=>m.LastName)
    <br>
    @Html.TextBoxFor(m=>m.LastName)
    @Html.ValidationMessageFor(model => model.LastName, "", new { @class = "text-danger" })

    . . .

    <input type="submit" value="Save">
}

Controller :

[HttpPost]
public ActionResult Index(DatabaseModel model)
{
    if (ModelState.IsValid)
    {
        ListToDatatable convert = new ListToDatatable();
        DataTable user = convert.Convert(model);
        DatabaseRepository dbRepo = new DatabaseRepository();
        dbRepo.Upload(user);
    }
    return View(model);
}