编译Expression <T>时,是否隐式缓存？

Question

当Expression<T>被编译,是由框架隐式缓存由此得到的代码？我正在考虑静态Regex方法,其中框架隐式编译并缓存最后几个正则表达式.

如果没有缓存编译Expression<T>对象,您是否可以推荐一些最佳实践来保持编译时间,或者如果我手动缓存表达式,可能会导致问题的任何问题？

public MyResultType DoSomething(int arg1, int arg2)
{
    var result = invokeHandler(
        (IDoSomethingHandler h) => h.DoSomething(arg1, arg2)
    );
    return result;
}

private TResult invokeHandler<T, TResult>(Expression<Func<T, TResult>> action)
    where T : class
{
    // Here, I might want to check to see if action is already cached.

    var compiledAction = action.Compile();
    var methodCallExpr = action as MethodCallExpression;

    // Here, I might want to store methodCallExpr in a cache somewhere.

    var handler = ServiceLocator.Current.GetInstance<T>();
    var result = compiledAction(handler);

    return result;
}

在这个例子中,我有点担心如果我缓存编译的表达式,它将使用arg1和编译表达式时的值arg2,而不是从堆栈中的适当位置检索这些值(即而不是获得当前值).

Answer 1

没有; 我不相信它; 如果你想要它被缓存,你必须保持Delegate引用(通常Func<...>或Action<...>).同样,如果要获得最佳性能,可以将其编译为参数化表达式,以便在调用它时发送不同的值.

在这种情况下,重新措辞会有所帮助:

public MyResultType DoSomething(int arg1, int arg2)
{
    var result = invokeHandler(
        (IDoSomethingHandler h, int a1, int a2) => h.DoSomething(a1, a2),
        arg1, arg2);
    return result;
}

private TResult invokeHandler<T, TResult>(Expression<Func<T,int,int,TResult>> action,
    int arg1, int arg2)
    where T : class
{
    // Here, I might want to check to see if action is already cached.

    var compiledAction = action.Compile();
    var methodCallExpr = action as MethodCallExpression;

    // Here, I might want to store methodCallExpr in a cache somewhere.

    var handler = ServiceLocator.Current.GetInstance<T>();
    var result = compiledAction(handler, arg1, arg2);

    return result;
}

即,使表达式的数字参数,并在运行时传递实际的(而不是表达式中的常量).