MetadataType问题

Question

我正在使用VS2008 SP1，WCF Ria服务2009年7月CTP。我发现MetadataType不能在部分类模式下工作，真的不知道我错过了什么：

工作：-

public partial class Person
{
    private string _Name;

    [Required(AllowEmptyStrings=false, ErrorMessage="Name required entry")]
    [StringLength(3)]
    public string Name
    {
        set{_Name = value;}
        get{return _Name;}
    }
}

class Program
{
    static void Main(string[] args)
    {
        Person p = new Person { Name="123432" };
        List res = new List();
        Validator.TryValidateObject(p,new ValidationContext(p,null,null),
            res,true);
        if (res.Count > 0)
        {
            Console.WriteLine(res[0].ErrorMessage);
            Console.ReadLine();
        }
    }
}

不工作

public partial class Person
{
    private string _Name;

    public string Name
    {
        set{_Name = value;}
        get{return _Name;}
    }
}

[MetadataType(typeof(PersonMetadata))]
public partial class Person
{
}


public partial class PersonMetadata
{
    [Required(AllowEmptyStrings=false, ErrorMessage="Name required entry")]
    [StringLength(3)]
    public string Name;
}

class Program
{
    static void Main(string[] args)
    {
        Person p = new Person { Name="123432" };
        List res = new List();
        Validator.TryValidateObject(p,new ValidationContext(p,null,null),
            res,true);
        if (res.Count > 0)
        {
            Console.WriteLine(res[0].ErrorMessage);
            Console.ReadLine();
        }
    }
}

Answer 1

编辑：我在这里找到了答案：http://forums.silverlight.net/forums/p/149264/377212.aspx

验证前，需要手动注册元数据类：

TypeDescriptor.AddProviderTransparent(
            new AssociatedMetadataTypeTypeDescriptionProvider(typeof(Person), typeof(PersonMetadata)), typeof(Person));

        List<ValidationResult> res = new List<ValidationResult>();
        bool valid = Validator.TryValidateObject(p, new ValidationContext(p, null, null), res, true);

(原答案如下)

问题并不是特定于您的分部类，而是Validator.TryValidateObject似乎无法识别MetaDataType属性。我也有同样的问题--MVC2中的内置验证可以识别元数据类，但是TryValidateObject不能。

查看这些：Validating DataAnnotations with Validator class Validation does not work when I use Validator.TryValidateObject

顺便说一句，我不知道这是否有必要，但我见过的元数据类的所有示例都在每个属性上使用默认的get/set：

[Required(AllowEmptyStrings=false, ErrorMessage="Name required entry")]
[StringLength(3)]
public string Name { get; set; }

Answer 2

非常感谢Jeremy Gruenwald上面的答案。我完全被困在这个问题上了。

我想基于这个解决方案创建一个标准的验证类，但我不想传入元数据类类型，因为它让人感觉很难看。

为了实现这一点，我创建了一个静态类，它在自定义属性上进行查找以获得元数据类类型，然后在返回验证结果之前注册该类。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;

namespace MyApp.Validation
{
    public static class EntityValidator
    {
        public static List<ValidationResult> Validate(object instance, bool validateAllProperties = true)
        {
            RegisterMetadataClass(instance);

            var validationContext = new ValidationContext(instance, null, null);
            var validationResults = new List<ValidationResult>();

            Validator.TryValidateObject(instance, validationContext, validationResults, validateAllProperties);

            return validationResults;
        }

        private static void RegisterMetadataClass(object instance)
        {
            var modelType = instance.GetType();
            var metadataType = GetMetadataType(modelType);

            if (metadataType != null) 
            {
                TypeDescriptor.AddProviderTransparent(new AssociatedMetadataTypeTypeDescriptionProvider(modelType, metadataType), modelType);
            }
        }

        private static Type GetMetadataType(Type type)
        {
            var attribute = (MetadataTypeAttribute)type.GetCustomAttributes(typeof (MetadataTypeAttribute), true).FirstOrDefault();
            return attribute == null ? null : attribute.MetadataClassType;
        }
    }
}

用法很简单，如下所示：

var errors = EntityValidator.Validate(myEntity);

Answer 3

如果你正在使用WPF和EF，这对我来说一直是有效的…

[MetadataType(typeof(Department.Metadata))]
public partial class Department : BaseModel
{
    static Department()
    {
        TypeDescriptor.AddProvider(new AssociatedMetadataTypeTypeDescriptionProvider(typeof(Department),typeof(Metadata)), typeof(Department));
    }
    private sealed class Metadata
    {
        [Required(AllowEmptyStrings = false, ErrorMessage = "Department Name is required.")]
        [StringLength(50, ErrorMessage = "Name must be between 3 and 50 characters.", MinimumLength = 3)]
        public string Name;

        [StringLength(250, ErrorMessage = "Name must be between 10 and 250 characters.", MinimumLength = 10)]
        public string Description;
    }
}

以及实现它的基类...

public abstract class BaseModel : IDataErrorInfo
{
    #region Validation
    string IDataErrorInfo.Error
    {
        get { return null; }
    }
    string IDataErrorInfo.this[string propertyName]
    {
        get
        {
            var propertyInfo = GetType().GetProperty(propertyName);
            var results = new List<ValidationResult>();
            var result = Validator.TryValidateProperty(propertyInfo.GetValue(this, null), new ValidationContext(this, null, null)
            {
                MemberName = propertyName
            }, results);

            if (result) return string.Empty;
            var validationResult = results.First();
            return validationResult.ErrorMessage;
        }
    }
    #endregion
}