How to get a field name from an instance variable

Question

Please tell me about how to get a field name from an instance variable.

public class MainClass
{
    public void output()
    {
        Action valAction = new TestClass().testAction;

        //I want to output string 'testAction' from valAction variable here
        Debug.WriteLine(valAction.????);
    }
}

public class TestClass
{
    public Action testAction = () => { };
}

Community · Accepted Answer · 2017-03-20 10:29:34Z

1

Sounds like you have an XY Problem.

Fact is, it is not possible to do literally what you want. Once you have copied the value that your field testAction holds into a different variable (the local variable valAction), the original field is no longer involved.

Consider the simpler example:

class A
{
    int i = 17;

    void M()
    {
        int j = i;
    }
}

Would you expect to be able to somehow glean "i" from the variable j? I hope not. The variable j holds a 32-bit integer value. It doesn't care where that value came from, nor should it.

Similarly valAction doesn't hold any information about where the value it received came from. It holds only the value itself.

If you can explain the broader problem you're trying to address here, you may be able to get a solution. But there is none to the question you've asked here. You are literally asking for the impossible.

edited Mar 20, 2017 at 10:29

CommunityBot

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answered Mar 7, 2017 at 4:43

Peter Duniho

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2 Comments

kyouno Over a year ago

When I substitute named Function for a variable of valAction, I am as follows. {Method = {Void namedFunction()}} However, I am as follows when I substitute Lambda. I do not know which Lambda you show in this. {Method = {Void <.ctor>b__1_0()}} Therefore I want to know member variable name 'testAction'.

Peter Duniho Over a year ago

@kyounoii: "I want to know member variable name 'testAction'" -- you can't. That's what I'm saying. You are confusing the delegate instance itself, from which you could extract the method target name, with the variable that stores the delegate instance. When the delegate instance is assigned to any other variable, it in no way remains related to the variable that it was assigned from.

Humble · Accepted Answer · 2017-03-07 04:30:13Z

0

Replace

Debug.WriteLine(valAction.????);

with

Debug.WriteLine((Type.GetType(a.ToString()).GetMember("testAction"))[0]);

answered Mar 7, 2017 at 4:30

Humble

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2 Comments

Peter Duniho Over a year ago

What is a in the above? How does this, in any way, address the question that was asked? If you have to specify the string literal "testAction", how is this better than just calling Debug.WriteLine("testAction");?

kyouno Over a year ago

I want to come out without using literal 'testAction'

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