MVC.NET Core 中的条件验证（RequiredIf）

Question

我正在尝试有条件地验证 MVC.NET Core 中的字段。我有两个单选按钮。如果我选择是（对于所有权），我想在下面填写一个必填字段（活动下拉菜单）但是，无论我如何努力，要验证的值始终来自 Activity 字段，而不是来自 Ownership 字段（“N\A”而不是“Yes”）有人可以告诉我我做错了什么吗视图 (chtml)<div class=" form-group">    <div class="bisformdynamiclabel"></div>    <br />    @Html.RadioButtonFor(model => model.BIS232Request.JSONData.OwnershipActivity.Ownership, "Yes", new { id = "OwnershipAnswer_true", onclick = "displayOwnershipFieldsRow(true)" })    <label for="OwnershipAnswer_true">Yes</label>    @Html.RadioButtonFor(model => model.BIS232Request.JSONData.OwnershipActivity.Ownership, "No", new { id = "OwnershipAnswer_false", onclick = "displayOwnershipFieldsRow(false)" })    <label for="OwnershipAnswer_false">No</label>    <span class="alert-danger">        @Html.ValidationMessage("OwnershipAnswer")    </span></div><div class="row ownershipfieldsrow">    <div class="col-xs-12 col-md-12">        <div class=" form-group">            <div class="bisformdynamiclabel"></div>            <br />            <input style="display:none" class="form-control" type="text" asp-for="BIS232Request.JSONData.OwnershipActivity.Activity" />            <select class="form-control ownershipactivityselect" onchange="$('#BIS232Request_JSONData_OwnershipActivity_Activity').val($(this).val());  ">                <option value="N/A">Please Select</option>                <option value="Manufacturer">Manufacturer</option>                <option value="Distributor">Distributor</option>                <option value="Exporter">Exporter</option>                <option value="Importer">Importer</option>                <option value="Other">Other</option>            </select>            <span asp-validation-for="BIS232Request.JSONData.OwnershipActivity.Activity" class="alert-danger"></span>            <span class="alert-danger">                @Html.ValidationMessage("OwnershipAnswerActivity")            </span>        </div>    </div>

Answer 1

基于最初的实现，我建议扩展RequiredAttribute而不是ValidationAttribute- 然后根据 [Required] 设置默认的 ErrorMessage 和其他默认值。无论哪种方式，“errormessage”属性都是多余的，因为您已经将其作为属性，ValidationAttribute并且原始代码会为该属性生成警告ErrorMessage- 您也可以将nameof其用于属性装饰，以使代码中的内容更加紧凑：

我的实现稍微更具体一些，因此如果一个属性是布尔值，我可以指示一个属性是必需的（如果勾选了一个复选框）：

[AttributeUsage(AttributeTargets.Property)]

public class RequiredIfTrueAttribute : RequiredAttribute

{

    private string PropertyName { get; set; }

    public RequiredIfTrueAttribute(string propertyName)

    {

        PropertyName = propertyName;

    }

    protected override ValidationResult IsValid(object value, ValidationContext context)

    {

        object instance = context.ObjectInstance;

        Type type = instance.GetType();

        bool.TryParse(type.GetProperty(PropertyName).GetValue(instance)?.ToString(), out bool propertyValue);

        if (propertyValue && string.IsNullOrWhiteSpace(value?.ToString()))

        {

            return new ValidationResult(ErrorMessage);

        }

        return ValidationResult.Success;

    }

}

示例用法：

public bool IsBusinessProfile { get; set; }

[RequiredIfTrue(nameof(IsBusinessProfile), ErrorMessage = "ABN is required for Business Profiles")]

public string Abn { get; set; }

Answer 2

我建立在 Rob 提供的答案之上。这是一个通用验证器，而不是继承自Required，并且还提供客户端验证。我正在使用.Net Core 3.0

using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;

using System;

using System.Collections.Generic;

using System.Text;

namespace System.ComponentModel.DataAnnotations

{

    [AttributeUsage(AttributeTargets.Property)]

    public class RequiredIfTrueAttribute : ValidationAttribute, IClientModelValidator

    {

        private string PropertyName { get; set; }

        public RequiredIfTrueAttribute(string propertyName)

        {

            PropertyName = propertyName;

            ErrorMessage = "The {0} field is required."; //used if error message is not set on attribute itself

        }

        protected override ValidationResult IsValid(object value, ValidationContext context)

        {

            object instance = context.ObjectInstance;

            Type type = instance.GetType();

            bool.TryParse(type.GetProperty(PropertyName).GetValue(instance)?.ToString(), out bool propertyValue);

            if (propertyValue && (value == null || string.IsNullOrWhiteSpace(value.ToString())))

            {

                return new ValidationResult(ErrorMessage);

            }

            return ValidationResult.Success;

        }

        public void AddValidation(ClientModelValidationContext context)

        {

            MergeAttribute(context.Attributes, "data-val", "true");

            var errorMessage = FormatErrorMessage(context.ModelMetadata.GetDisplayName());

            MergeAttribute(context.Attributes, "data-val-requirediftrue", errorMessage);

        }

        private bool MergeAttribute(IDictionary<string, string> attributes, string key, string value)

        {

            if (attributes.ContainsKey(key))

            {

                return false;

            }

            attributes.Add(key, value);

            return true;

        }

    }

}

客户端 Javascript

//Custom validation script for the RequiredIfTrue validator

/*

 * Note that, jQuery validation registers its rules before the DOM is loaded. 

 * If you try to register your adapter after the DOM is loaded, your rules will

 * not be processed. So wrap it in a self-executing function.

 * */

(function ($) {

    var $jQval = $.validator;

   $jQval.addMethod("requirediftrue",

       function (value, element, parameters) {

            return value !== "" && value != null;

        }

    );

    var adapters = $jQval.unobtrusive.adapters;

    adapters.addBool('requirediftrue');

})(jQuery);

用法

    public bool IsSpecialField { get; set; }

    [RequiredIfTrue(nameof(IsSpecialField), ErrorMessage="This is my custom error message")]

    [Display(Name = "Address 1")]

    public string Address1 { get; set; }

    [RequiredIfTrue(nameof(IsSpecialField))]

    public string City { get; set; }

Answer 3

另一种更简洁、更通用的方法是实现更通用的属性，而不是特定的“requiredIf”属性，因为您必须为碰巧使用的每种验证类型创建多个自定义属性。

幸运的是，从 .NET Core 2 开始，Microsoft 提供了IPropertyValidationFilter可以在自定义属性上实现的接口。这个接口定义了一个函数ShouldValidateEntry，它允许控制当前条目是否应该被验证；所以这在调用任何验证器之前运行。

框架中已经有一个默认实现，即ValidateNeverAttribute，但是实现您自己的对另一个值进行条件检查是微不足道的：

using System;

using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;

namespace Foo {

    // Implementation makes use of the IPropertyValidationFilter interface that allows

    // control over whether the attribute (and its children, if relevant) need to be

    // validated.

    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]

    public class ConditionalValidationAttribute : Attribute, IPropertyValidationFilter {

        public string OtherProperty { get; set; }

        public object OtherValue { get; set; }

        public ConditionalValidationAttribute(string otherProperty, object otherValue) {

            OtherProperty = otherProperty;

            OtherValue = otherValue;

        }

        public bool ShouldValidateEntry(ValidationEntry entry, ValidationEntry parentEntry) {

            // Default behaviour if no other property is set: continue validation

            if (string.IsNullOrWhiteSpace(OtherProperty)) return true;

            // Get the property specified by the name. Might not properly work with

            // nested properties.

            var prop = parentEntry.Metadata.Properties[OtherProperty]?.PropertyGetter?.Invoke(parentEntry.Model);

            return prop == OtherValue;

        }

    }

}

只需使用此属性注释相关属性，任何验证器，以及您自己实现的自定义验证器，只会在必要时调用！