Use nameof() to access parent object name

Question

I have an extension method which takes a parameter. Inside the extension method I want to get access to the name of the object which was passed in.

static MyObject Add<T>(this MyObject myObj, T value) {
    // MyObject is dictionary<string, object> for simple example
    myObj.Add(nameof(value), value);
    return myObj;
}

void run() {
  var anotherObject = new AnotherObject() { Name = "Bob" };
  var myObject = new MyObject().Add(anotherObject.Field);
}

When this executes it puts "value", "Bob" whereas i want it to put "Name", "Bob" in the dictionary.

Is this possible using the nameof() function or do I need to re-think the logic? The only thing i can come up with to preserve the general idea is:

static MyObject Add<T>(this MyObject myObj, string name, T value)...

myObject.Add(nameOf(anotherObject.Field), anotherObject.Field);

I didn't like having to repeat the field definition.

if you use nameof() the name has to be known at compile time. You can use reflection to access type names at runtime. If you need to call a generic method with the type you reflected you can use https://msdn.microsoft.com/en-us/library/system.reflection.methodinfo.makegenericmethod(v=vs.110).aspx — Dennis Kuypers, Aug 24 '17 at 16:03
I only scanned the question, disregard the comment and see my answer :) — Dennis Kuypers, Aug 24 '17 at 16:10
It is not possible, for the simple reason that the parameter value does not necessarily even come from a variable with a name. For non-by-reference (i.e. not `out` or `ref`) parameters, _any_ value, generated by _any_ means (a variable, expression, method call, property getter, etc.), which is of the appropriate type can be passed. Only some of the value sources even have a name. It doesn't make any sense whatsoever to ask what the name of the passed value is. — Peter Duniho, Aug 24 '17 at 19:00

score 0 · Answer 1 · answered Aug 24 '17 at 16:09

0

You can access the type name using typeof()

static MyObject Add<T>(this MyObject myObj, T value) {
    // MyObject is dictionary<string, object> for simple example
    myObj.Add(typeof(T).Name, value);
    return myObj;
}

answered Aug 24 '17 at 16:09

Dennis Kuypers

546
4
16

score 0 · Answer 2 · answered Aug 24 '17 at 16:17

Sample below should help you out.

    //MyObject class

    public class MyObject{
     public string Name{get;set;}
    }

//AnotherObject class

    public class AnotherObject{
    public string Name{get;set;}
    }

//Method call

    void Main()
    {
      var anotherObject = new AnotherObject() { Name = "Bob" };
      var object1 = new MyObject();
      var obj = object1.Add<MyObject, AnotherObject>(object1, anotherObject);
     //print obj.Name; anywhere.
    }

//Extension Method

    static class Ext{
    public static MyObject Add<K,T>(this MyObject myObj, MyObject myObjOne, T value) {
        // MyObject is dictionary<string, object> for simple example
        string val = typeof(T).GetProperty("Name").GetValue(value).ToString();
        myObjOne.Name = val;
        return myObjOne;
    }

    }

Use nameof() to access parent object name

2 Answers2