Hot get the name of an object?

Question

Possible Duplicate:
print name of the variable in c#

How I can print the name of any object

MyClass c1, c2;

printName(c1);
printName(c2);

void printName(Object o)
{
    Console.WriteLine("name of object : "+ o.???());
}

output should be like this:

name of object : c1
name of object : c2

This is specific to .Net, but answer for other platform/language can be helpful.

Answer 1

That is not possible.
Name of the variable is of importance only to the developer (not the compiler or runtime).

You could create a Dictionary<string, object> & add those instances with the name of their variable to achieve something like that.

EDIT: And that is the reason, it is said - write code for people to understand and incidentally for the compiler.

Answer 2

The name doesn't exist outside of the source code - to do this, you would have to be attached to yourself as a debugger, or dig through the PDBs. In short, this not practical in any measure for C# and most other languages.

Answer 3

This is impossible.

What is the result of this?

string s = "Hello, world!";
string t = s;
printName(t);

As s and t both refer to the same instance of string there is no way to distinguish between invocations of printName with s as the parameter versus t as the parameter.

And what should be the result of this?

printName("Hello, world!");

Answer 4

I don't think it's theoretically possible. Think about this scenario:

MyClass a, b;
a = new MyClass();
b = a;

Console.WriteLine("name of b is " + SomeMagicClass.GetVarName(b));
//Should it be "b" or "a"?

I am sure there is a better explanation involving generated MIDL code along the lines of variable name not even being present at runtime.

EDIT Alas I was wrong. Inspired by Jon Skeet's post about Null Reference exception handling and suddenly being reminded about projection there is a way to kinda do that.

Here is complete working codez:

public static class ObjectExtensions {
    public static string GetVariableName<T>(this T obj) {
        System.Reflection.PropertyInfo[] objGetTypeGetProperties = obj.GetType().GetProperties();

        if(objGetTypeGetProperties.Length == 1)
            return objGetTypeGetProperties[0].Name;
        else
            throw new ArgumentException("object must contain one property");
    }
}

class Program {
    static void Main(string[] args) {
        string strName = "sdsd";
        Console.WriteLine(new {strName}.GetVariableName());

        int intName = 2343;
        Console.WriteLine(new { intName }.GetVariableName());
    }
}

Answer 5

That does not make sense for the following reason:

The object itself is in memory and has no name. You are accessing it using a reference which has a name. Thus, the reference name can change in any moment, you can have 50 references "pointing" to the same nameless object, etc.

Consider this:

MyClass c1, c2;
c1 = new MyClass();
c2 = c1;
printName(c1);
printName(c2);

As you can see, both c1 and c2 are references to the exact same object which has no way of "knowing" who is referencing it or by which name.

Answer 6

You need to place a Name property inside your MyClass class, eg.

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

  // rest of class goes here
  // ...
}

then you can use it as follows:

var c1 = new MyClass() { Name = "c1" };
var c2 = new MyClass() { Name = "c2" };

printName(c1);
printName(c2);

void printName(MyClass o)
{
    Console.WriteLine("name of object : "+ o.Name);
}