Question

我读了一篇关于expando对象here的文章，但我希望实现不同的东西我想在运行时添加带有动态属性的属性对象，将值放在上面然后检索：

    private static readonly ConditionalWeakTable<object, ExpandoObject> props = new ConditionalWeakTable<object, ExpandoObject>();
    public static void AddDataExtension(this object key, dynamic value)
    {
        props.Add(key, value);
    }

    public static dynamic GetDataExtension(this object key)
    {
        ExpandoObject ex = null;
        return props.TryGetValue(key, out ex);
    }

用法：

'Insert data at runtime'
instance.AddDataExtension("Hello", "hi");

'Get the data at runtime'
instance.GetDataExtension("Hello")

但是我收到了这个错误：

The best overloaded method match for 'System.Runtime.CompilerServices.ConditionalWeakTable<object,System.Dynamic.ExpandoObject>.Add(object, System.Dynamic.ExpandoObject)' has some invalid arguments

我觉得我误用了这个属性，这有可能实现吗？如果有，怎么样？请帮忙。

修改

这是完整的课程：

public static class instance
{
    private static readonly ConditionalWeakTable<object, ExpandoObject> props = new ConditionalWeakTable<object, ExpandoObject>();
        public static void AddDataExtension(this object key, dynamic value)
        {
            props.Add(key, value);
        }

        public static dynamic GetDataExtension(this object key)
        {
            ExpandoObject ex = null;
            return props.TryGetValue(key, out ex);
        } 
}

我想要达到的目的是：
我会随机变量，例如“photo_01, photo_12, photo_15, name_01, name_02, age_01, age_02” 如果可能，我想以这种方式使用该方法：

id = <fetch from dbase>
instance.AddDataExtension("photo_" + id, byte[]);

然后检索值：

instance.GetDataExtension("photo_" + id)

Answer 1

我没有看到你从ExpandoObject继承，所以你可能需要这样做。 ExpandoObject具有很好的基础结构，可用于创建动态类型。

这是一篇关于创建动态类型的更详细的文章： http://www.codeproject.com/Articles/62839/Adventures-with-C-4-0-dynamic-ExpandoObject-Elasti

Answer 2

使用conditionalWeakTable和dynamics，您可以在几行中实现动态扩展属性：

using System.Dynamic;
using System.Runtime.CompilerServices;

namespace ExtensionProperties
{
    /// <summary>
    /// Dynamically associates properies to a random object instance
    /// </summary>
    /// <example>
    /// var jan = new Person("Jan");
    ///
    /// jan.Age = 24; // regular property of the person object;
    /// jan.DynamicProperties().NumberOfDrinkingBuddies = 27; // not originally scoped to the person object;
    ///
    /// if (jan.Age &lt; jan.DynamicProperties().NumberOfDrinkingBuddies = 27)
    /// Console.WriteLine("Jan drinks too much");
    /// </example>
    /// <remarks>
    /// If you get 'Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create' you should reference Microsoft.CSharp
    /// </remarks>
    public static class ObjectExtensions
    {
        ///<summary>Stores extended data for objects</summary>
        private static ConditionalWeakTable<object, object> extendedData = new ConditionalWeakTable<object, object>();

        /// <summary>
        /// Gets a dynamic collection of properties associated with an object instance,
        /// with a lifetime scoped to the lifetime of the object
        /// </summary>
        /// <param name="obj">The object the properties are associated with</param>
        /// <returns>A dynamic collection of properties associated with an object instance.</returns>
        public static dynamic DynamicProperties(this object obj) => extendedData.GetValue(obj, _ => new ExpandoObject());
    }
}

用法示例在xml注释中：

var jan = new Person("Jan");

jan.Age = 24; // regular property of the person object;
jan.DynamicProperties().NumberOfDrinkingBuddies = 27; // not originally scoped to the person object;

if (jan.Age && jan.DynamicProperties().NumberOfDrinkingBuddies == 27)
{
    Console.WriteLine("Jan drinks too much");
}

Answer 3

因为ExpandoObject是密封的，所以不可能。

如何在运行时在expando上添加对象属性？

3 个答案: