c# - 使用 PropertyDescriptor 确定属性是否为复杂对象

Question

我正在尝试在 WCF 服务中进行一些验证，为此我正在使用 WCFDataAnnotations我通过 this post 找到的

问题是它不能递归验证，所以对于嵌套对象它不起作用。这么说吧

[DataContract]
public class Model
{
    [DataMember]
    [Required(ErrorMessage = "RequiredOne is required")]
    public string RequiredOne { get; set; }

    [DataMember]
    [StringLength(10, ErrorMessage = "Not Required should be at most 10 characters long")]
    public string NotRequired { get; set; }

    [DataMember]
    [Required(ErrorMessage = "ChildModel is required")]
    public ChildModel ChildModel { get; set; }

}

[DataContract]
public class ChildModel
{
    [DataMember]
    [Required(ErrorMessage = "RequiredValue is required")]
    public string RequiredValue { get; set; } 

    [DataMember]
    public string NotRequiredValue { get; set; }

}

它不会准确地获得所需的 childModel RequiredValue。

所以我查看了那个 dll 的源代码并试图让它工作。实际代码是

public class DataAnnotationsObjectValidator : IObjectValidator
{
    public IEnumerable<ValidationResult> Validate(object input)
    {
        if (input == null) return Enumerable.Empty<ValidationResult>();

        return from property in TypeDescriptor.GetProperties(input).Cast<PropertyDescriptor>()
               from attribute in property.Attributes.OfType<ValidationAttribute>()
               where !attribute.IsValid(property.GetValue(input))
               select new ValidationResult
               (
                   attribute.FormatErrorMessage(string.Empty),
                   new[] { property.Name }
               );
    }
} 

所以我想把它改成这样

public IEnumerable<ValidationResult> Validate(object input)
{
    if (input == null) return Enumerable.Empty<ValidationResult>();

    var validationResults = new List<ValidationResult>();

    foreach (var prop in TypeDescriptor.GetProperties(input).Cast<PropertyDescriptor>())
    {
        foreach (var att in prop.Attributes.OfType<ValidationAttribute>())
        {
            //This doesn't work, it's one of the several 
            //attempts I've made
            if (prop.ComponentType.IsClass)
                Validate(prop.ComponentType);

            if (!att.IsValid(prop.GetValue(input)))
            {
                validationResults.Add(new ValidationResult(
                        att.FormatErrorMessage(string.Empty),
                        new[] { prop.Name }
                ));
            }
        }
    }

    return validationResults;
}

目的是检查是否有任何属性是复杂的，如果是复杂的则递归地验证自身，但我不确定如何检查给定的“props”是否已转换为 TypeDescriptors。

谢谢

Answer 1

在我看来，下面的代码应该可以解决问题:

public IEnumerable<ValidationResult> Validate(object input)
{
    return ValidateWithState(input, new HashSet<object>());
}

private IEnumerable<ValidationResult> ValidateWithState(object input, HashSet<object> traversedInputs)
{
    if (input == null || traversedInputs.Contains(input))
    {
       return Enumerable.Empty<ValidationResult>();
    }

    var validationResults = new List<ValidationResult>();

    foreach (var prop in TypeDescriptor.GetProperties(input).Cast<PropertyDescriptor>())
    {
        foreach (var att in prop.Attributes.OfType<ValidationAttribute>())
        {
            if (!att.IsValid(prop.GetValue(input)))
            {
                validationResults.Add(new ValidationResult(
                        att.FormatErrorMessage(string.Empty),
                        new[] { prop.Name }
            ));
        }

        traversedInputs.Add(input);

        if (prop.PropertyType.IsClass || prop.PropertyType.IsInterface))
        {
            validationResults.AddRange(ValidateWithState(prop.GetValue(input), traversedInputs));
        }
    }

    return validationResults;
}

可能不是最优雅的解决方案，但我认为它会奏效。