使用数据注释的有条件的必需属性

Question

我有一个这样的课程：

public class Document
{
   public int DocumentType{get;set;}

   [Required]
   public string Name{get;set;}

   [Required]
   public string Name2{get;set;}
}

现在，如果我在[Required]和Name属性上添加Name2数据注释，那么一切正常，如果Name或Name2为空，验证会抛出错误。

但如果Name等于1，我只需要DocumentType字段 只有在Name2等于2时才需要DocumentType。

public class Document
{
   public int DocumentType{get;set;}

   [Required(Expression<Func<object, bool>>)]
   public string Name{get;set;}

   [Required(Expression<Func<object, bool>>)]
   public string Name2{get;set;}
}

但我知道我不能，它会导致错误。我该怎么办这个要求？

Answer 1

RequiredIf验证属性

我写了一个RequiredIfAttribute，当另一个属性具有某个值（您需要的）时，或者当另一个属性 某个特定值时，需要特定的属性值

这是可能有用的代码：

/// <summary>
/// Provides conditional validation based on related property value.
/// </summary>
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public sealed class RequiredIfAttribute : ValidationAttribute
{
    #region Properties

    /// <summary>
    /// Gets or sets the other property name that will be used during validation.
    /// </summary>
    /// <value>
    /// The other property name.
    /// </value>
    public string OtherProperty { get; private set; }

    /// <summary>
    /// Gets or sets the display name of the other property.
    /// </summary>
    /// <value>
    /// The display name of the other property.
    /// </value>
    public string OtherPropertyDisplayName { get; set; }

    /// <summary>
    /// Gets or sets the other property value that will be relevant for validation.
    /// </summary>
    /// <value>
    /// The other property value.
    /// </value>
    public object OtherPropertyValue { get; private set; }

    /// <summary>
    /// Gets or sets a value indicating whether other property's value should match or differ from provided other property's value (default is <c>false</c>).
    /// </summary>
    /// <value>
    ///   <c>true</c> if other property's value validation should be inverted; otherwise, <c>false</c>.
    /// </value>
    /// <remarks>
    /// How this works
    /// - true: validated property is required when other property doesn't equal provided value
    /// - false: validated property is required when other property matches provided value
    /// </remarks>
    public bool IsInverted { get; set; }

    /// <summary>
    /// Gets a value that indicates whether the attribute requires validation context.
    /// </summary>
    /// <returns><c>true</c> if the attribute requires validation context; otherwise, <c>false</c>.</returns>
    public override bool RequiresValidationContext
    {
        get { return true; }
    }

    #endregion

    #region Constructor

    /// <summary>
    /// Initializes a new instance of the <see cref="RequiredIfAttribute"/> class.
    /// </summary>
    /// <param name="otherProperty">The other property.</param>
    /// <param name="otherPropertyValue">The other property value.</param>
    public RequiredIfAttribute(string otherProperty, object otherPropertyValue)
        : base("'{0}' is required because '{1}' has a value {3}'{2}'.")
    {
        this.OtherProperty = otherProperty;
        this.OtherPropertyValue = otherPropertyValue;
        this.IsInverted = false;
    }

    #endregion

    /// <summary>
    /// Applies formatting to an error message, based on the data field where the error occurred.
    /// </summary>
    /// <param name="name">The name to include in the formatted message.</param>
    /// <returns>
    /// An instance of the formatted error message.
    /// </returns>
    public override string FormatErrorMessage(string name)
    {
        return string.Format(
            CultureInfo.CurrentCulture,
            base.ErrorMessageString,
            name,
            this.OtherPropertyDisplayName ?? this.OtherProperty,
            this.OtherPropertyValue,
            this.IsInverted ? "other than " : "of ");
    }

    /// <summary>
    /// Validates the specified value with respect to the current validation attribute.
    /// </summary>
    /// <param name="value">The value to validate.</param>
    /// <param name="validationContext">The context information about the validation operation.</param>
    /// <returns>
    /// An instance of the <see cref="T:System.ComponentModel.DataAnnotations.ValidationResult" /> class.
    /// </returns>
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (validationContext == null)
        {
            throw new ArgumentNullException("validationContext");
        }

        PropertyInfo otherProperty = validationContext.ObjectType.GetProperty(this.OtherProperty);
        if (otherProperty == null)
        {
            return new ValidationResult(
                string.Format(CultureInfo.CurrentCulture, "Could not find a property named '{0}'.", this.OtherProperty));
        }

        object otherValue = otherProperty.GetValue(validationContext.ObjectInstance);

        // check if this value is actually required and validate it
        if (!this.IsInverted && object.Equals(otherValue, this.OtherPropertyValue) ||
            this.IsInverted && !object.Equals(otherValue, this.OtherPropertyValue))
        {
            if (value == null)
            {
                return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName));
            }

            // additional check for strings so they're not empty
            string val = value as string;
            if (val != null && val.Trim().Length == 0)
            {
                return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName));
            }
        }

        return ValidationResult.Success;
    }
}

Answer 2

使用数据注释的有条件要求的属性

 [RequiredIf(dependent Property name, dependent Property value)]

e.g. 


 [RequiredIf("Country", "Ethiopia")]
 public string POBox{get;set;}
 // POBox is required in Ethiopia
 public string Country{get;set;}

 [RequiredIf("destination", "US")]
 public string State{get;set;}
 // State is required in US

 public string destination{get;set;}



public class RequiredIfAttribute : ValidationAttribute
{
    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)
    {
        var field = validationContext.ObjectType.GetProperty(_dependentProperty);
        if (field != null)
        {
            var dependentValue = field.GetValue(validationContext.ObjectInstance, null);
            if ((dependentValue == null && _targetValue == null) || (dependentValue.Equals(_targetValue)))
            {
                if (!_innerAttribute.IsValid(value))
                {
                    string name = validationContext.DisplayName;
                    return new ValidationResult(ErrorMessage=name + " Is required.");
                }
            }
            return ValidationResult.Success;
        }
        else
        {
            return new ValidationResult(FormatErrorMessage(_dependentProperty));
        }
    }
}

Answer 3

开箱即用，我认为这仍然不可能。

但我发现这个promising article about Mvc.ValidationToolkit （也是here，遗憾的是this只是alpha，但您可能也只是从此代码中提取所需的方法并将其集成到您自己的中，它包含了很好的声音属性RequiredIf，它似乎与您的原因完全匹配：

• 您从linked zip下载项目并构建它
• 从您的构建文件夹中获取内置的dll，并在您正在使用的项目中引用它
• 遗憾的是，这似乎也需要引用MVC（最简单的方法就是在VS中启动MVC项目或install-package Microsoft.AspNet.Mvc）
• 在您要使用它的文件中，添加using Mvc.ValidationToolkit;
• 然后您可以编写[RequiredIf("DocumentType", 2)]或[RequiredIf("DocumentType", 1)]之类的内容，因此只要name或name2都不提供DocumentType或{{1}}，对象就有效不等于1或2

Answer 4

查看Fluent验证

https://www.nuget.org/packages/FluentValidation/

项目描述 一个.NET的小型验证库，它使用流畅的接口和lambda表达式为您的业务对象构建验证规则。

https://github.com/JeremySkinner/FluentValidation

Answer 5

查看MVC Foolproof验证。如果我没记错的话，它在模型中有数据注释，如 RequiredIf（依赖属性，依赖值）。您可以从以下网址下载Foolproof：
Visual Studio（2017） - ＆gt;工具 - ＆gt; Nuget包管理器 - ＆gt;管理解决方案的Nuget包。除了jquery文件之外，还可以参考mvcfoolproof.unobtrusive.min.js。

Answer 6

签出ExpressiveAnnotations .net库 Git reference

它具有“ RequiredIf”和“ AssertThat”验证属性

Answer 7

我一直使用System.ComponentModel.DataAnnotations中的已实现IValidatableObject;

以下示例

  public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
        {
            if (this.SendInAppNotification)
            {
                if (string.IsNullOrEmpty(this.NotificationTitle) || string.IsNullOrWhiteSpace(this.NotificationTitle))
                {
                    yield return new ValidationResult(
                        $"Notification Title is required",
                        new[] { nameof(this.NotificationTitle) });
                }
            }

Answer 8

我通过扩展 RequiredAttribute 类解决了这个问题，借用了 CompareAttribute 和 Robert's excellent solution 的一些逻辑：

/// <summary>
/// Provides conditional <see cref="RequiredAttribute"/> 
/// validation based on related property value.
/// </summary>
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public sealed class RequiredIfAttribute : RequiredAttribute
{
    /// <summary>
    /// Gets or sets a value indicating whether other property's value should
    /// match or differ from provided other property's value (default is <c>false</c>).
    /// </summary>
    public bool IsInverted { get; set; } = false;

    /// <summary>
    /// Gets or sets the other property name that will be used during validation.
    /// </summary>
    /// <value>
    /// The other property name.
    /// </value>
    public string OtherProperty { get; private set; }

    /// <summary>
    /// Gets or sets the other property value that will be relevant for validation.
    /// </summary>
    /// <value>
    /// The other property value.
    /// </value>
    public object OtherPropertyValue { get; private set; }

    /// <summary>
    /// Initializes a new instance of the <see cref="RequiredIfAttribute"/> class.
    /// </summary>
    /// <param name="otherProperty">The other property.</param>
    /// <param name="otherPropertyValue">The other property value.</param>
    public RequiredIfAttribute(string otherProperty, object otherPropertyValue)
        : base()
    {
        OtherProperty = otherProperty;
        OtherPropertyValue = otherPropertyValue;
    }

    protected override ValidationResult IsValid(
        object value, 
        ValidationContext validationContext)
    {
        PropertyInfo otherPropertyInfo = validationContext
            .ObjectType.GetProperty(OtherProperty);
        if (otherPropertyInfo == null)
        {
            return new ValidationResult(
                string.Format(
                    CultureInfo.CurrentCulture, 
                    "Could not find a property named {0}.", 
                validationContext.ObjectType, OtherProperty));
        }

        // Determine whether to run [Required] validation
        object actualOtherPropertyValue = otherPropertyInfo
            .GetValue(validationContext.ObjectInstance, null);
        if (!IsInverted && Equals(actualOtherPropertyValue, OtherPropertyValue) ||
            IsInverted && !Equals(actualOtherPropertyValue, OtherPropertyValue))
        {
            return base.IsValid(value, validationContext);
        }
        return default;
    }
}

示例用法：

public class Model {
    public bool Subscribe { get; set; }
    
    [RequiredIf(nameof(Subscribe), true)]
    [DataType(DataType.EmailAddress)]
    public string Email { get; set; }
}

通过这种方式，您可以获得所有标准的 Required 验证功能。

注意：我使用的是 .NET 5，但我试图删除在 c# 9.0 中添加的语言功能以实现更广泛的兼容性。

Answer 9

我不能完全按照你的要求给你，但你有没有考虑过以下内容？

public abstract class Document // or interface, whichever is appropriate for you
{
    //some non-validted common properties
}

public class ValidatedDocument : Document
{
    [Required]
    public string Name {get;set;}
}

public class AnotherValidatedDocument : Document
{
    [Required]
    public string Name {get;set;}

    //I would suggest finding a descriptive name for this instead of Name2, 
    //Name2 doesn't make it clear what it's for
    public string Name2 {get;set;}
}

public class NonValidatedDocument : Document
{
    public string Name {get;set;}
}

//Etc...

理由是int DocumentType变量。对于需要处理的每个“类型”文档，可以使用具体的子类类型来替换它。这样做可以更好地控制属性注释。

在不同的情况下，似乎只需要一些属性，这可能表示您的文档类试图做得太多，并支持上述建议。