不引人注目的验证 C# MVC Razor

是否可以进行不显眼的验证，使某个字段成为必填字段，但前提是其他属性发生更改？

例如

[Required]
public Decimal Income {get; set;}
[Required]
public Decimal Tax {get; set;}
//Required if tax or income changes
public string ChangeReason {get; set;}

我考虑过拥有多个后备存储字段并编写一个自定义验证器来比较它们，但想知道是否有人有更好的建议？

自定义验证器是正确的选择。不久前我不得不构建类似的东西。

我设置了一个隐藏值 - “更改” - 每当用户修改感兴趣的字段时将其设置为 true。

对 2 个感兴趣的属性设置一个RequiredIf 验证器：

 [RequiredIf("Changed", true, ErrorMessage = "Required")]

requiredIf 验证器的代码如下所示：

public class RequiredIfAttribute : ValidationAttribute, IClientValidatable
{
    private RequiredAttribute _innerAttribute = new RequiredAttribute();

    public string DependentProperty { get; set; }
    public object TargetValue { get; set; }

    public RequiredIfAttribute(string dependentProperty, object targetValue)
    {
        this.DependentProperty = dependentProperty;
        this.TargetValue = targetValue;
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        // get a reference to the property this validation depends upon
        var containerType = validationContext.ObjectInstance.GetType();
        var field = containerType.GetProperty(this.DependentProperty);

        if (field != null)
        {
            // get the value of the dependent property
            var dependentvalue = field.GetValue(validationContext.ObjectInstance, null);

            // compare the value against the target value
            if ((dependentvalue == null && this.TargetValue == null) ||
                (dependentvalue != null && dependentvalue.Equals(this.TargetValue)))
            {
                // match => means we should try validating this field
                if (!_innerAttribute.IsValid(value))
                    // validation failed - return an error
                    return new ValidationResult(this.ErrorMessage, new[] { validationContext.MemberName });
            }
        }

        return null;
    }

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        var rule = new ModelClientValidationRule()
        {
            ErrorMessage = FormatErrorMessage(metadata.GetDisplayName()),
            ValidationType = "requiredif",
        };

        string depProp = BuildDependentPropertyId(metadata, context as ViewContext);

        // find the value on the control we depend on;
        // if it's a bool, format it javascript style 
        // (the default is True or False!)
        string targetValue = (this.TargetValue ?? "").ToString();
        if (this.TargetValue.GetType() == typeof(bool))
            targetValue = targetValue.ToLower();

        rule.ValidationParameters.Add("dependentproperty", depProp);
        rule.ValidationParameters.Add("targetvalue", targetValue);

        yield return rule;
    }

    private string BuildDependentPropertyId(ModelMetadata metadata, ViewContext viewContext)
    {
        // build the ID of the property
        string depProp = viewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(this.DependentProperty);
        // unfortunately this will have the name of the current field appended to the beginning,
        // because the TemplateInfo's context has had this fieldname appended to it. Instead, we
        // want to get the context as though it was one level higher (i.e. outside the current property,
        // which is the containing object (our Person), and hence the same level as the dependent property.
        var thisField = metadata.PropertyName + "_";
        if (depProp.StartsWith(thisField))
            // strip it off again
            depProp = depProp.Substring(thisField.Length);
        return depProp;
    }
}

JavaScript：

/// <reference path="jquery-1.4.4-vsdoc.js" />
/// <reference path="jquery.validate.unobtrusive.js" />

$.validator.addMethod('requiredif',
function (value, element, parameters) {
    var id = '#' + parameters['dependentproperty'];

    // get the target value (as a string, 
    // as that's what actual value will be)
    var targetvalue = parameters['targetvalue'];
    targetvalue =
      (targetvalue == null ? '' : targetvalue).toString();

    // get the actual value of the target control
    // note - this probably needs to cater for more 
    // control types, e.g. radios
    var control = $(id);
    var controltype = control.attr('type');
    var actualvalue =
        controltype === 'checkbox' ?
        control.attr('checked').toString() :
        control.val();

    // if the condition is true, reuse the existing 
    // required field validator functionality
    if (targetvalue === actualvalue)
        return $.validator.methods.required.call(
          this, value, element, parameters);

    return true;
 }
 );

 $.validator.unobtrusive.adapters.add(
'requiredif',
['dependentproperty', 'targetvalue'],
function (options) {
    options.rules['requiredif'] = {
        dependentproperty: options.params['dependentproperty'],
        targetvalue: options.params['targetvalue']
    };
    options.messages['requiredif'] = options.message;
});