有没有办法创建委托来获取和设置FieldInfo的值？ [英] Is there a way to create a delegate to get and set values for a FieldInfo?

问题描述

对于属性，有 GetGetMethod 和 GetSetMethod ，以便我可以做到：

For properties there are GetGetMethod and GetSetMethod so that I can do:

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

和

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

但是，如何解决 FieldInfo s ？

But how do I go about FieldInfos?

我不是在寻找代表 GetValue 和 SetValue （这意味着我每次都会引用反射）

I am not looking for delegates to GetValue and SetValue (which means I will be invoking reflection each time)

Getter = s => (T)fieldInfo.GetValue(s);
Setter = (s, t) => (T)fieldInfo.SetValue(s, t);

但如果有一个 CreateDelegate ？ 我的意思是由于分配返回值，我可以治疗分配像一个方法？如果是这样，它有一个 MethodInfo 句柄？换句话说，如何传递正确的 MethodInfo 设置并从成员字段获取值到 CreateDelegate 方法，以便我得到一个代理，我可以直接读取和写入字段

but if there is a CreateDelegate approach here? I mean since assignments return a value, can I treat assignments like a method? If so is there a MethodInfo handle for it? In other words how do I pass the right MethodInfo of setting and getting a value from a member field to CreateDelegate method so that I get a delegate back with which I can read and write to fields directly?

Getter = (Func<S, T>)Delegate.CreateDelegate(typeof(Func<S, T>), fieldInfo.??);
Setter = (Action<S, T>)Delegate.CreateDelegate(typeof(Action<S, T>), fieldInfo.??);

我可以构建表达式并编译它，但我正在寻找更简单的东西。最后，如果没有问题的回答，我不介意去表达路线，如下所示：

I can build expression and compile it, but I am looking for something simpler. In the end I don't mind going the expression route if there is no answer for the asked question, as shown below:

var instExp = Expression.Parameter(typeof(S));
var fieldExp = Expression.Field(instExp, fieldInfo);
Getter = Expression.Lambda<Func<S, T>>(fieldExp, instExp).Compile();
if (!fieldInfo.IsInitOnly)
{
    var valueExp = Expression.Parameter(typeof(T));
    Setter = Expression.Lambda<Action<S, T>>(Expression.Assign(fieldExp, valueExp), instExp, valueExp).Compile();
}

或者我不在之后（因为我没有看到类似的东西）？

Or am I after the nonexistent (since I have nowhere seen something like that yet) ?

推荐答案

字段访问不是通过一个方法（如getters和setter）执行的 - 它是用IL指令执行的 - 所以没有什么可以将分配给一个代表。您必须使用表达式路由来创建可以分配给代理的代码（实际上是IL）的块。

Field access isn't performed via a method (like getters and setters)--it's performed with an IL instruction--so there's nothing you can assign to a delegate. you'll have to use the expression route to create a "block" of code (effectively IL) that can be assigned to a delegate.

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