8

我有一个 ExpandoObject 我要发送到一个外部库方法，该方法需要一个对象。从我所见，这个外部库在内部使用 TypeDescriptor.GetProperties，这似乎会导致我的 ExpandoObject 出现一些问题。

我可以改用匿名对象，这似乎可行，但使用 ExpandoObject 对我来说更方便。

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

想法？

更新

除了下面 somedave 的答案（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);
    }
}

并像这样注册它：

dynamic parameters = new ExpandoObject();
TypeDescriptor.AddProvider(new ExpandoObjectTypeDescriptionProvider(), parameters);
4

2 回答 2

10

实现 ICustomTypeDescriptor 实际上并不难。这是我从使用 WinForms 属性网格（使用 TypeDescriptor 和 PropertyDescriptor）所做的一些工作中改编而来的一些示例代码。诀窍是还实现一个适当的 PropertyDescriptor 类，您可以从ICustomTypeDescriptor.GetProperties(). 值得庆幸的是，ExpandoObject 通过实现IDictionary<string, object>对它的键和值的动态检索使这变得非常简单。请记住，这可能会或可能不会正常工作（我没有测试过），并且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; }
        }
    }
}
于 2013-05-15T14:41:52.463 回答
0

我可以让 OP 的代码与 Marc 的 ExpandoTypeDescriptor 代码一起工作的唯一方法是修改 OP 对 GetTypeDescriptor 的调用，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);
}
于 2020-09-18T12:47:12.433 回答