如何获取元数据自定义属性？

问题描述：

我有一个在类级别定义数据注释的类。元数据类具有与之关联的自定义属性，以及通常的DisplayName，DisplayFormat等。

I have a class that defines data annotations at class level. The meta data class has custom attributes associated with it, along with the usual DisplayName, DisplayFormat etc.

public class BaseMetaData
{
    [DisplayName("Id")]
    public object Id { get; set; }

    [DisplayName("Selected")]
    [ExportItem(Exclude = true)]
    public object Selected { get; set; }
}

[MetadataType(typeof(BaseMetaData))]
public class BaseViewModel
{
    public int Id { get; set; }
    public bool Selected { get; set; }

给出类型 T ，如何从中检索自定义属性元数据类？下面的尝试不起作用，因为元数据属性来自 BaseViewModel ，而不是来自 BaseMetaData 类。

Given a type T, how can I retrieve the custom attributes from the meta data class? The attempt below would not work as the metadata properties are from the BaseViewModel rather than the BaseMetaData class.

需要可以正常工作，即不能执行typeof（BaseMetaData）.GetProperty（e.PropertyName）。想知道是否存在一种从类中获取MetadataType的方法，那么它将使其成为可能。

Needs to work generically i.e. can't do typeof(BaseMetaData).GetProperty(e.PropertyName). Wondering if there is a way of getting the MetadataType from the class then it would make it possible.

var type = typeof (T);
var metaData = ModelMetadataProviders.Current.GetMetadataForType(null, type);

var propertMetaData = metaData.Properties
    .Where(e =>
    {
        var attribute = type.GetProperty(e.PropertyName)
            .GetCustomAttributes(typeof(ExportItemAttribute), false)
            .FirstOrDefault() as ExportItemAttribute;
        return attribute == null || !attribute.Exclude;
    })
    .ToList();

答

通过使用MetadataTypeAttribute的类型获取解决方案

Found a solution by using the type of MetadataTypeAttribute to get the custom attributes.

var type = typeof (T);
var metadataType = type.GetCustomAttributes(typeof(MetadataTypeAttribute), true)
    .OfType<MetadataTypeAttribute>().FirstOrDefault();
var metaData = (metadataType != null)
    ? ModelMetadataProviders.Current.GetMetadataForType(null, metadataType.MetadataClassType)
    : ModelMetadataProviders.Current.GetMetadataForType(null, type);

var propertMetaData = metaData.Properties
    .Where(e =>
    {
        var attribute = metaData.ModelType.GetProperty(e.PropertyName)
            .GetCustomAttributes(typeof(ExportItemAttribute), false)
            .FirstOrDefault() as ExportItemAttribute;
        return attribute == null || !attribute.Exclude;
    })
    .ToList();

如何获取元数据自定义属性？

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