如何使用反射通过其属性值之一获取属性名称或如何获取当前正在验证的数据属性的属性信息？

Question

我想编写自定义验证属性并向验证结果添加具有验证错误的其他成员名称。问题是我想根据属性名称和无效的匹配属性索引或键（我想验证 IEnumerables 或 IDictionaries）动态生成成员名称，例如Names[0]、等Names[1]。Names[key]例如：

模型：

public class ModelClass
{
    [ItemMaxLength(10)]
    [Display(ResourceType = typeof(CategoriesRename), Name = "CategoryNamesFieldName")]
    public IDictionary<string, string> Names { get; set; }
}

属性：

public class ItemMaxLengthAttribute : ValidationAttribute
{
    private readonly int _maxLength = int.MaxValue;

    public ItemMaxLengthAttribute(int maxLength)
    {
        _maxLength = maxLength;
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        ...
        // I can get instance and it's type from validation context
        var instance = validationContext.ObjectInstance; // which is instance of ModelClass
        var instanceType = validationContext.ObjectType; //which is typeof(ModelClass)
        var dispayName = validationContext.DisplayName; //which is value of Display attribute
        ...
    }
}

所以主要的想法是（我不喜欢它）让当前属性通过它的DysplayName属性值（dispayName）进行验证。我有点被困在这里一段时间了。也许还有其他方法来获取正在验证的属性的属性信息吗？

PS我已经尝试过MemberName财产，正如Alexandre Rondeau建议的那样，但问题是validationContext.MemberName = null它无法使用。MSDN还说这个属性代表实体成员名称，而不是相应数据字段的名称，我需要相应数据字段的名称。

Answer 1

使用该代码，两个测试都通过，因此 MemberName 不为空。

[TestClass]
public class RefectionInValidationTest
{
    [TestMethod]
    public void GivenAModelWithItemMaxAttributeOnFieldName_WhenValidating_ThenModelClassIsValid()
    {
        //Arange
        var validModelClass = new ModelClass();
        var validations = new Collection<ValidationResult>();

        //Act
        var isValid = Validator.TryValidateObject(validModelClass, new ValidationContext(validModelClass, null, null), validations, true);

        //Assert
        Assert.IsTrue(isValid);
    }

    [TestMethod]
    public void GivenAModelWithItemMaxAttributeOnFieldNotName_WhenValidating_ThenModelClassIsInvalid()
    {
        //Arange
        var invalidaModelClass = new InvalidModelClass();
        var validations = new Collection<ValidationResult>();

        //Act
        var isValid = Validator.TryValidateObject(invalidaModelClass, new ValidationContext(invalidaModelClass, null, null), validations, true);

        //Assert
        Assert.IsFalse(isValid);
    }
}

public class ModelClass
{
    [ItemMaxLength(10)]
    public IDictionary<string, string> Names { get; set; }
}
public class InvalidModelClass
{
    [ItemMaxLength(10)]
    public IDictionary<string, string> NotNames { get; set; }
}

public class ItemMaxLengthAttribute : ValidationAttribute
{
    private readonly int _maxLength = int.MaxValue;

    public ItemMaxLengthAttribute(int maxLength)
    {
        _maxLength = maxLength;
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var propretyInfo = validationContext.ObjectType.GetProperty(validationContext.MemberName);
        if (propretyInfo.Name == "Names")
            return ValidationResult.Success;

        return new ValidationResult("The property isn't 'Names'");
    }
}