获取EX pression树里面的方法参数的值 [英] Getting the values of method parameters inside expression trees
问题描述
我瞎搞与前pression树,不过我有点卡住了。
I'm messing around with expression trees, but I'm little stuck.
我有这样的EX pression:
I have this expression:
Expression<Func<IX, int>> expr = i => i.GetAll(1, b, method());
其中:
int b = 2;
public static int method()
{
return 3;
}
public interface IX
{
int GetAll(int a, int b, int c);
}
现在我想的方法和参数的值,该方法的名称。该方法的名称是很容易的,但参数值是困难的部分。我知道我可以分析他们自己,但我需要处理所有的情况下( ConstantEx pression
, MemberEx pression
, MethodCallEx pression
,也许更多的,我不知道)。所以我在想,如果有一般的方式来获得它们的值。如1,2,3
Now I want to get name of the method and values of parameters for this method. Name of the method is easy, but parameter values are harder part. I know I can parse them myself, but I would need to handle all cases (ConstantExpression
, MemberExpression
, MethodCallExpression
and maybe more I'm not aware of). So I was thinking if there was "general" way to get their values. eg 1, 2, 3.
推荐答案
您可以得到 MethodCallEx pression
的有问题的争论
并创建编译 Func键&LT;对象&gt;
- 从他们(拳击的价值类型,如果必要的话),然后可以计算
You can get the arguments of the MethodCallExpression
in question
and create compiled Func<object>
s from them (boxing value-types if necessary), which can then be evaluated.
例如:
var args = from arg in ((MethodCallExpression)expr.Body).Arguments
let argAsObj = Expression.Convert(arg, typeof(object))
select Expression.Lambda<Func<object>>(argAsObj, null)
.Compile()();
这显然会炸毁如果EX pression的身体不是一个方法调用前pression或任何参数的方法不能被评价为是(例如,如果它们依赖于参数前pression)。
This will obviously blow up if the expression's body is not a method-call expression or if any of the arguments to the method cannot be evaluated as is (e.g. if they depend on the argument to the expression).
很明显,你可以做一个更好的工作,如果你知道的参数类型的方法,事前。为了您的具体的例子,这应该工作:
Obviously, you can do a better job if you know the types of the arguments to the method beforehand. For your specific example, this should work:
var args = from arg in ((MethodCallExpression)expr.Body).Arguments
select Expression.Lambda<Func<int>>(arg, null)
.Compile()();
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