Question

我有一个ExpandoObject，我将其发送到一个带有对象的外部库方法。从我看到的这个外部lib内部使用TypeDescriptor.GetProperties，这似乎导致我的ExpandoObject出现一些问题。

我可以使用匿名对象，这似乎有效，但使用ExpandoObject更方便。

我是否需要构建自己的DynamicObject并通过实现ICustomTypeDescriptor自己处理它，或者我在这里遗漏了什么。

想法？

更新

除了以下somedave的回答（根据评论），我添加了这个类

public class ExpandoObjectTypeDescriptionProvider : TypeDescriptionProvider
{
    private static readonly TypeDescriptionProvider m_Default = TypeDescriptor.GetProvider(typeof(ExpandoObject));

    public ExpandoObjectTypeDescriptionProvider()
        :base(m_Default)
    {
    }

    public override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance)
    {
        var defaultDescriptor = base.GetTypeDescriptor(objectType, instance);

        return instance == null ? defaultDescriptor :
            new ExpandoObjectTypeDescriptor(instance);
    }
}

并将其注册为：

dynamic parameters = new ExpandoObject();
TypeDescriptor.AddProvider(new ExpandoObjectTypeDescriptionProvider(), parameters);

Answer 1

实现ICustomTypeDescriptor实际上并不是那么难。下面是我使用WinForms属性网格（使用TypeDescriptor和PropertyDescriptor）进行的一些工作改编的示例代码。诀窍是还要实现一个适当的PropertyDescriptor类，您可以从ICustomTypeDescriptor.GetProperties()传回来。值得庆幸的是，ExpandoObject通过实现IDictionary<string, object>来动态检索它的键和值，使这变得非常简单。请记住，这可能会或可能不会正常工作（我还没有测试过），它可能不适用于具有大量嵌套属性的ExpandoObjects。

public class ExpandoTypeDescriptor : ICustomTypeDescriptor
{
    private readonly ExpandoObject _expando;

    public ExpandoTypeDescriptor(ExpandoObject expando)
    {
        _expando = expando;
    }

    // Just use the default behavior from TypeDescriptor for most of these
    // This might need some tweaking to work correctly for ExpandoObjects though...

    public string GetComponentName()
    {
        return TypeDescriptor.GetComponentName(this, true);
    }

    public EventDescriptor GetDefaultEvent()
    {
        return TypeDescriptor.GetDefaultEvent(this, true);
    }

    public string GetClassName()
    {
        return TypeDescriptor.GetClassName(this, true);
    }

    public EventDescriptorCollection GetEvents(Attribute[] attributes)
    {
        return TypeDescriptor.GetEvents(this, attributes, true);
    }

    EventDescriptorCollection System.ComponentModel.ICustomTypeDescriptor.GetEvents()
    {
        return TypeDescriptor.GetEvents(this, true);
    }

    public TypeConverter GetConverter()
    {
        return TypeDescriptor.GetConverter(this, true);
    }

    public object GetPropertyOwner(PropertyDescriptor pd)
    {
        return _expando;
    }

    public AttributeCollection GetAttributes()
    {
        return TypeDescriptor.GetAttributes(this, true);
    }

    public object GetEditor(Type editorBaseType)
    {
        return TypeDescriptor.GetEditor(this, editorBaseType, true);
    }

    public PropertyDescriptor GetDefaultProperty()
    {
        return null;
    }

    // This is where the GetProperties() calls are
    // Ignore the Attribute for now, if it's needed support will have to be implemented
    // Should be enough for simple usage...

    PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties()
    {
        return ((ICustomTypeDescriptor)this).GetProperties(new Attribute[0]);
    }

    public PropertyDescriptorCollection GetProperties(Attribute[] attributes)
    {
        // This just casts the ExpandoObject to an IDictionary<string, object> to get the keys
        return new PropertyDescriptorCollection(
            ((IDictionary<string, object>)_expando).Keys
            .Select(x => new ExpandoPropertyDescriptor(((IDictionary<string, object>)_expando), x))
            .ToArray());
    }

    // A nested PropertyDescriptor class that can get and set properties of the
    // ExpandoObject dynamically at run time
    private class ExpandoPropertyDescriptor : PropertyDescriptor
    {
        private readonly IDictionary<string, object> _expando;
        private readonly string _name;

        public ExpandoPropertyDescriptor(IDictionary<string, object> expando, string name)
            : base(name, null)
        {
            _expando = expando;
            _name = name;
        }

        public override Type PropertyType
        {
            get { return _expando[_name].GetType(); }
        }

        public override void SetValue(object component, object value)
        {
            _expando[_name] = value;
        }

        public override object GetValue(object component)
        {
            return _expando[_name];
        }

        public override bool IsReadOnly
        {
            get
            {
                // You might be able to implement some better logic here
                return false;
            }
        }

        public override Type ComponentType
        {
            get { return null; }
        }

        public override bool CanResetValue(object component)
        {
            return false;
        }

        public override void ResetValue(object component)
        {
        }

        public override bool ShouldSerializeValue(object component)
        {
            return false;
        }

        public override string Category
        {
            get { return string.Empty; }
        }

        public override string Description
        {
            get { return string.Empty; }
        }
    }
}

Answer 2

我可以使OP的代码与Marc的ExpandoTypeDescriptor代码一起使用的唯一方法是修改OP对GetTypeDescriptor的调用，并将返回值转换为ExpandoObject。

public override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance)
{
     var defaultDescriptor = base.GetTypeDescriptor(objectType, instance);

     return instance == null ? defaultDescriptor :
            new ExpandoTypeDescriptor((ExpandoObject)instance);
}

公开ExpandoObject的属性

2 个答案: