使用数据注释使复选框成为必需

Question

我想向用户显示消息，如果未选中复选框，他必须在提交表单后接受条款，如果选中复选框，则提交表单。

我的模型上有这个代码：

public class UserClass
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required(ErrorMessage = "Entry ID")]
    public int ID { get; set; }
    [Required(ErrorMessage = "Entry Name")]
    public string Name { get; set; }
}

控制器：

private readonly ApplicationUserClass _auc;
public abcController(ApplicationUserClass auc)
{
    _auc = auc;
}

public IActionResult Index()
{
    return View();
}

public IActionResult Create()
{
    return View();
}

[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(UserClass uc)
{
    _auc.Add(uc);
    _auc.SaveChanges();
    return View();
}

查看：

<div class="row">
    <div class="col-md-9">
        <form asp-action="Create">
            <div asp-validation-summary="ModelOnly" class="text-danger"></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="Name" class="control-label"></label>
                <input asp-for="Name" class="form-control" />
                <span asp-validation-for="Name" class="text-danger"></span>
            </div>

            <div class="form-group">
                <div class="col-md-offset-2 col-md-10">
                    <input type="submit" value="sumbit" class="btn btn-primary" />
                </div>
            </div>
            <b>@ViewBag.message</b>
        </form>
    </div>
</div>

我看到了很多例子，但没有用。谁能给点建议？

Answer 1

您可以参考以下示例：

1. 创建一个 UserViewModel 来在 View 和控制器之间传输数据：

    public class UserViewModel
    {
        [Required(ErrorMessage = "Entry ID")]
        public int ID { get; set; }
        [Required(ErrorMessage = "Entry Name")]
        public string Name { get; set; } 
        //use custom validation method
        [CheckBoxRequired(ErrorMessage ="Please checked the items")]
        public bool IsAccepted { get; set; } 
    }
   

2. 添加自定义验证方法：

    public class CheckBoxRequired : ValidationAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            //get the entered value
            var student = (UserViewModel)validationContext.ObjectInstance;
            //Check whether the IsAccepted is selected or not.
            if (student.IsAccepted == false)
            { 
                //if not checked the checkbox, return the error message.
                return new ValidationResult(ErrorMessage == null ? "Please checked the checkbox" : ErrorMessage); 
            }
            return  ValidationResult.Success;
        }
    }
   

3. 创建 Action 方法来创建用户并使用 UserViewModel 在 View 和 Controller 之间传输数据。

        public IActionResult CreateUser()
        {
            return View();
        }
        [HttpPost]
        public IActionResult CreateUser(UserViewModel user)
        {
            if (ModelState.IsValid)
            {
               //after validation success, create a UserClass instance based on the ViewModel, and insert the "newuser" into database.
                var newuser = new UserClass();
                newuser.ID = user.ID;
                newuser.Name = user.Name;       
                //save the newuser into the database via dbcontext
                _dbcontext.UserClass.Add(newuser);
                _dbcontext.SaveChanges();
                return RedirectToAction(nameof(Index));
            }
            return View();
        }
   

4. 创建一个 CreateUser 视图页面：

        @model WebApplication2.Models.UserViewModel
   
        @{
            ViewData["Title"] = "CreateUser";
            Layout = "~/Views/Shared/_Layout.cshtml";
        } 
        <div class="row">
            <div class="col-md-6">
                <form asp-action="CreateUser">
                    <div asp-validation-summary="ModelOnly" class="text-danger"></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="Name" class="control-label"></label>
                        <input asp-for="Name" class="form-control" />
                        <span asp-validation-for="Name" class="text-danger"></span>
                    </div>
                    <div class="form-group form-check">
                        <label class="form-check-label">
                            <input class="form-check-input" asp-for="IsAccepted" /> @Html.DisplayNameFor(model => model.IsAccepted)
   
                        </label>
                        <span asp-validation-for="IsAccepted" class="text-danger"></span>
                    </div> 
                    <div class="form-group">
                        <input type="submit" value="Create" class="btn btn-primary" />
                    </div>
                </form>
            </div>
        </div> 
   
        @section Scripts {
            @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
        }
   

然后，截图如下：

Answer 2

这可以通过一个用于验证布尔值的新 Attribute 类来完成，然后将其放置在一个新的布尔属性上。

示例属性类：

public class MustBeTrueAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        if (value == null) return false;
        if (value is bool b) return b;

        throw new InvalidOperationException("Can only be used on boolean properties.");
    }
}

使用布尔属性扩展 UserClass，包括新的属性：

public class UserClass
{
    // existing properties here

    // new property -->
    [MustBeTrue(ErrorMessage = "You need to accept the terms")]
    public bool Accepted { get; set; }
}

将新元素添加到视图中：

<div class="form-group">
    <label asp-for="Accepted" class="control-label"></label>
    <input asp-for="Accepted" class="form-control" />
    <span asp-validation-for="Accepted" class="text-danger"></span>
</div>

最后，修改你的 Controller Post 动作方法来检查模型是否有效：

[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(UserClass uc)
{
    if (!ModelState.IsValid)
        return View(uc);

    _auc.Add(uc);
    _auc.SaveChanges();
    return View(uc);
}

最后一点：
我将Accepted 属性添加到类UserClass 中，您可以使用它与MVC 交互并保存到数据库中。
但是，您可能不希望在您的数据库表中拥有这个新属性。
如果是这种情况，那么您将需要引入一个 UserModel 类来与 MVC 交互（with Accepted 属性）并保持 UserClass 没有 Accepted 属性，然后添加代码以在加载和显示数据时从 UserClass 映射到 UserModel + 当从 MVC 接收到需要保存的数据时从 UserModel 映射到 UserClass 的代码。

Answer 3

我创建 ViewModel 调用 UserViewModel

 public class UserViewModel
    {
    //store DB for record
        public UserClass userClass { get; set; }
    //store Attribute class for validating boolean values
        public AttributeClass attributeClass { get; set; }

    }

  Controller

    private readonly ApplicationUserClass _auc;
public abcController(ApplicationUserClass auc)
{
    _auc = auc;
}

public IActionResult Index()
{
    return View();
}

public IActionResult Create()
{
    return View();
}

            [HttpPost]
            [ValidateAntiForgeryToken]
            public IActionResult Create(UserClass uc)
            {
                UserViewModel userViewModel = new UserViewModel() {
                  if (!ModelState.IsValid)
                    return View(uc);

                }
             

                _auc.Add(uc);
                _auc.SaveChanges();
                return View();
            }
        }



i don't know how to modify the controller logic. anybody can give advice? thanks