反射性能 - 创建代理(属性C#)

Question

我在使用反射时遇到了性能问题.
所以我决定为我的对象的属性创建委托,到目前为止得到了这个:

TestClass cwp = new TestClass();
var propertyInt = typeof(TestClass).GetProperties().Single(obj => obj.Name == "AnyValue");
var access = BuildGetAccessor(propertyInt.GetGetMethod());
var result = access(cwp);

static Func<object, object> BuildGetAccessor(MethodInfo method)
{
    var obj = Expression.Parameter(typeof(object), "o");

    Expression<Func<object, object>> expr =
        Expression.Lambda<Func<object, object>>(
            Expression.Convert(
                Expression.Call(
                    Expression.Convert(obj, method.DeclaringType),
                    method),
                typeof(object)),
            obj);

    return expr.Compile();
}

结果非常令人满意,比使用传统方法快30-40倍(PropertyInfo.GetValue (obj, null);)

问题是:我怎样才能创建SetValue一个属性相同的属性？不幸的是没有办法.

我这样做是因为我不能使用方法,<T>因为我的应用程序的结构.

Answer 1

这应该适合你:

static Action<object, object> BuildSetAccessor(MethodInfo method)
{
    var obj = Expression.Parameter(typeof(object), "o");
    var value = Expression.Parameter(typeof(object));

    Expression<Action<object, object>> expr =
        Expression.Lambda<Action<object, object>>(
            Expression.Call(
                Expression.Convert(obj, method.DeclaringType),
                method,
                Expression.Convert(value, method.GetParameters()[0].ParameterType)),
            obj,
            value);

    return expr.Compile();
}

用法:

var accessor = BuildSetAccessor(typeof(TestClass).GetProperty("MyProperty").GetSetMethod());
var instance = new TestClass();
accessor(instance, "foo");
Console.WriteLine(instance.MyProperty);

用TestClass:

public class TestClass 
{
    public string MyProperty { get; set; }
}

打印出来:

FOO

Answer 2

CreateDelegate如果性能是关键的话,我认为你的构造会更好.既然你知道方法的事先签名,在这里仅仅是GetGetMethod和GetSetMethod的PropertyInfo,你可以创建一个委托执行的方法很直接相同的签名.如果您需要为委托构建一些逻辑(您没有方法句柄),表达式将更适合.我在针对这个问题的不同路线上做了一些基准测试:

Func<S, T> Getter;
Action<S, T> Setter;
PropertyInfo Property;
public void Initialize(Expression<Func<S, T>> propertySelector)
{
    var body = propertySelector.Body as MemberExpression;
    if (body == null)
        throw new MissingMemberException("something went wrong");

    Property = body.Member as PropertyInfo;



    //approaches:

    //Getter = s => (T)Property.GetValue(s, null);

    //Getter = memberSelector.Compile();

    //ParameterExpression inst = Expression.Parameter(typeof(S));
    //Getter = Expression.Lambda<Func<S, T>>(Expression.Property(inst, Property), inst).Compile();

    //var inst = Expression.Parameter(typeof(S));
    //Getter = Expression.Lambda<Func<S, T>>(Expression.Call(inst, Property.GetGetMethod()), inst).Compile();

    //Getter = (Func<S, T>)Delegate.CreateDelegate(typeof(Func<S, T>), Property.GetGetMethod());



    //Setter = (s, t) => Property.SetValue(s, t, null);

    //var val = Expression.Parameter(typeof(T));
    //var inst = Expression.Parameter(typeof(S));
    //Setter = Expression.Lambda<Action<S, T>>(Expression.Call(inst, Property.GetSetMethod(), val),
    //                                         inst, val).Compile();

    //Setter = (Action<S, T>)Delegate.CreateDelegate(typeof(Action<S, T>), Property.GetSetMethod());
}


//Actual calls (tested under loop):
public T Get(S instance)
{
    //direct invocation:
    //return (T)Property.GetValue(instance, null);

   //calling the delegate:
   //return Getter(instance);
}
public void Set(S instance, T value)
{
    //direct invocation:
    //Property.SetValue(instance, value, null);

   //calling the delegate:
   //Setter(instance, value);
}

大约10000000个电话的结果 - (获取,设置):

GetValue-SetValue(直接):3800毫秒,5500毫秒

GetValue-SetValue(委托):3600毫秒,5300毫秒

编译表达式:

   Get: Expression.Property: 280 ms

        Expression.Call: 280 ms

        direct compile: 280 ms
   Set: 300 ms

创建委托:130毫秒,135毫秒

直接财产电话:70毫秒,70毫秒

在你的情况下,我会写:

public static Func<S, T> BuildGetAccessor<S, T>(Expression<Func<S, T>> propertySelector)
{
    return propertySelector.GetPropertyInfo().GetGetMethod().CreateDelegate<Func<S, T>>();
}

public static Action<S, T> BuildSetAccessor<S, T>(Expression<Func<S, T>> propertySelector)
{
    return propertySelector.GetPropertyInfo().GetSetMethod().CreateDelegate<Action<S, T>>();
}

// a generic extension for CreateDelegate
public static T CreateDelegate<T>(this MethodInfo method) where T : class
{
    return Delegate.CreateDelegate(typeof(T), method) as T;
}

public static PropertyInfo GetPropertyInfo<S, T>(this Expression<Func<S, T>> propertySelector)
{
    var body = propertySelector.Body as MemberExpression;
    if (body == null)
        throw new MissingMemberException("something went wrong");

    return body.Member as PropertyInfo;
}

所以现在你打电话:

TestClass cwp = new TestClass();
var access = BuildGetAccessor((TestClass t) => t.AnyValue);
var result = access(cwp);

不是那么简单吗？在这里写了一个通用类来处理确切的事情.