不使用 DynamicInvoke() 的快速委托访问器？

Question

我最近正在开发一个 SQLite ORM，并且遇到了一些关于动态事物的问题（我正在针对 C# 3.5 进行编码）。其中之一是关于如何快速获得房产价值。我尝试了许多不同的方法，其中一种非常快（几乎可以作为原生和硬编码访问），但问题是您需要使用泛型，而我只想提供类型。如果我只提供类型，我会被委托（只有缓慢而绝望的 DynamicInvoke 方法可用）或使用 MethodInfo.Invoke()...

所以我想知道当我有委托时是否有任何适当的方法来获取这个 Invoke()（而不是 DynamicInvoke）。我想将 Delegate 转换为 Func，但它不起作用。

有什么技巧吗？

class Program
{
    static void Main(String[] args)
    {
        DummyClass dummyInstance= new DummyClass();
        dummyInstance.DummyMember = "I'm a Dummy Value!";

        Type typeDummyClass = typeof(DummyClass);

        PropertyInfo propertyInfo = typeDummyClass.GetProperty("DummyMember");
        MethodInfo methodInfo = propertyInfo.GetGetMethod();

        ParameterExpression parameterExpression = Expression.Parameter(typeDummyClass, "Instance");
        Expression expression = Expression.Property(parameterExpression, propertyInfo.Name);

        Type funcType = typeof(Func<,>);
        Type funcGenericType = funcType.MakeGenericType(typeDummyClass, propertyInfo.PropertyType);

        LambdaExpression lambdaExpression = Expression.Lambda(funcGenericType, expression, parameterExpression);
        Expression<Func<DummyClass, String>> expressionTyped = Expression.Lambda<Func<DummyClass, String>>(expression, parameterExpression);
        Delegate @delegate = lambdaExpression.Compile();
        Func<DummyClass, String> func = expressionTyped.Compile();

        TimeSpan timeSpanNativeAccess = new TimeSpan(0);
        TimeSpan timeSpanGetValueCachedAccess = new TimeSpan(0);
        TimeSpan timeSpanMethodInfoCachedAccess = new TimeSpan(0);
        TimeSpan timeSpanDelegateCachedAccess = new TimeSpan(0);
        TimeSpan timeSpanFuncCachedAccess = new TimeSpan(0);

        for (UInt32 i = 0; i < 100000; i++)
        {
            Stopwatch stopwatchNativeAccess = Stopwatch.StartNew();
            var dummyNativeAccess = dummyInstance.DummyMember;
            stopwatchNativeAccess.Stop();

            Stopwatch stopwatchGetValueCachedAccess = Stopwatch.StartNew();
            var dummyGetValueCachedAccess = propertyInfo.GetValue(dummyInstance, null);
            stopwatchGetValueCachedAccess.Stop();

            Stopwatch stopwatchMethodInfoCachedAccess = Stopwatch.StartNew();
            var dummyMethodInfoCachedAccess = methodInfo.Invoke(dummyInstance, null);
            stopwatchMethodInfoCachedAccess.Stop();

            Stopwatch stopwatchDelegateCachedAccess = Stopwatch.StartNew();
            var dummyDelegateCachedAccess = @delegate.DynamicInvoke(dummyInstance);
            stopwatchDelegateCachedAccess.Stop();

            Stopwatch stopwatchFuncCachedAccess = Stopwatch.StartNew();
            var dummyFuncCachedAccess = func.Invoke(dummyInstance); // func(dummyInstance);
            stopwatchFuncCachedAccess.Stop();

            timeSpanNativeAccess += stopwatchNativeAccess.Elapsed;
            timeSpanGetValueCachedAccess += stopwatchGetValueCachedAccess.Elapsed;
            timeSpanMethodInfoCachedAccess += stopwatchMethodInfoCachedAccess.Elapsed;
            timeSpanDelegateCachedAccess += stopwatchDelegateCachedAccess.Elapsed;
            timeSpanFuncCachedAccess += stopwatchFuncCachedAccess.Elapsed;
        }

        Console.WriteLine("timeSpanNativeAccess = " + timeSpanNativeAccess.TotalMilliseconds + " ms");
        Console.WriteLine("timeSpanGetValueCachedAccess = " + timeSpanGetValueCachedAccess.TotalMilliseconds + " ms");
        Console.WriteLine("timeSpanMethodInfoCachedAccess = " + timeSpanMethodInfoCachedAccess.TotalMilliseconds + " ms");
        Console.WriteLine("timeSpanDelegateCachedAccess = " + timeSpanDelegateCachedAccess.TotalMilliseconds + " ms");
        Console.WriteLine("timeSpanFuncCachedAccess = " + timeSpanFuncCachedAccess.TotalMilliseconds + " ms");

        Console.ReadKey();
    }
}

public class DummyClass
{
    public String DummyMember { get; set; }
}

Answer 1

您好，我找到了一种使用此处提供的代码获取 Invoke() 方法的方法：Faster way to cast a Func<T, T2> to Func<T, object>?

诀窍在于 C# 3.5 不提供任何变化的东西，因此您必须在创建转换时自带转换。

随之添加一个 UnaryExpression 来带来转换，以便得到 Func（用于 getter）

private static Func<Object, Object> GenerateAccessor(MethodInfo methodInfo)
{
    Type typeObject = typeof(Object);

    ParameterExpression @object = Expression.Parameter(typeObject, "Objet");

    UnaryExpression unaryExpression = Expression.Convert(@object, methodInfo.DeclaringType);
    MethodCallExpression methodCallExpression = Expression.Call(unaryExpression, methodInfo);
    UnaryExpression unaryExpressionBis = Expression.Convert(methodCallExpression, typeObject);

    Expression<Func<Object, Object>> epxressionFuncObjectObject = Expression.Lambda<Func<Object, Object>>(unaryExpressionBis, @object);

    return epxressionFuncObjectObject.Compile();
}