在C＃中按名称获取和保留属性引用的最佳方法是什么

Question

I want to know if there is a better way (than what I'm currently doing) to obtain and hold a reference to a property in another object using only the object and property string names. Particularly, is there a better way to do this with the new dynamic functionality of .Net 4.0?

Here is what I have right now.

I have a " PropertyReference<T> " object that takes an object name and property name in the constructor.

An Initialize() method uses reflection to find the object and property and stores the property Getter as an Action<T> and the property Setter as an Func<T> .

When I want to actually call the property I do something like this:

int x = _propertyReference.Get();

or

_propertyReference.Set(2);

Here is my PropertyReference<T> code. Please dissect and make suggestions for improvement.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Xml;

namespace WindowsFormsApplication2
{
    public class PropertyReference<T> : IPropertyReference
    {
        public string ComponentName { get; set; }
        public string PropertyName { get; set; }
        public bool IsInitialized
        {
            get
            {
                return (_action != null && _func != null);
            }
        }

        Action<T> _action;
        Func<T> _func;

        public PropertyReference() { }

        public PropertyReference(string componentName, string propertyName)
        {
            ComponentName = componentName;
            PropertyName = propertyName;
        }

        public void Initialize(IEntity e)
        {            
            Object component = e.GetByName(ComponentName);
            if (component == null) return;

            Type t = e.GetByName(ComponentName).GetType();
            PropertyInfo pi = t.GetProperty(PropertyName);

            _action = (T a) => pi.SetValue(component, a, null);
            _func = () => (T)pi.GetValue(component, null);
        }

        public void Reset()
        {
            _action = null;
            _func = null;

        }

        public void Set(T value)
        {
            _action.Invoke(value);
        }

        public T Get()
        {
            return _func();
        }

    }
}

Note: I can't use the "Emit" functionality as I need this code to work on the new Windows Phone 7 and that does not support Emit.

UPDATE:

Just did some speed tests after replacing:

_action = (T a) => pi.SetValue(component, a, null);
_func = () => (T)pi.GetValue(component, null);

With

_action = Action<T>)Delegate.CreateDelegate(typeof(Action<T>),component,pi.GetSetMethod());
_func = (Func<T>)Delegate.CreateDelegate(typeof(Func<T>), component, pi.GetGetMethod());

As suggested by dtb below.

Tested by making 100,000 calls to the Get() property. Here are the results.

_func = () => (T)pi.GetValue(component, null)

took about 200ms

_func = (Func<T>)Delegate.CreateDelegate(typeof(Func<T>), component, pi.GetGetMethod());

took about 10ms

Huge difference. Wasn't expecting that, but cool!

Still open to more improvements.

Answer 1

You could obtain delegates directly representing the getter and setter method:

object component;
PropertyInfo pi;

_action = (Action<T>)Delegate.CreateDelegate(typeof(Action<T>),
                                             component,
                                             pi.GetSetMethod());

_func = (Func<T>)Delegate.CreateDelegate(typeof(Func<T>),
                                         component,
                                         pi.GetGetMethod());

Answer 2

It really depends on how often you're going to be calling it. If it isn't massive throughput, then fine - but note that the reflection-based GetValue / SetValue are pretty slow. You could cache the delegates, but another simple approach might be to look at HyperDescriptor - this uses the same API as PropertyDescriptor (so you again get GetValue / SetValue ), but it uses dynamic methods underneath. The API then is something like:

PropertyDescriptor prop = TypeDescriptor.GetProperties(type)["PropertyName"];

or

PropertyDescriptor prop = TypeDescriptor.GetProperties(obj)["PropertyName"];

then

object value = prop.GetValue(component);
prop.SetValue(component, newValue);