Question

For example,

static void Main()
{
    var someVar = 3;

    Console.Write(GetVariableName(someVar));
}

The output of this program should be:

someVar

How can I achieve that using reflection?

Answer 1

It is not possible to do this with reflection, because variables won’t have a name once compiled to IL. However, you can use expression trees and promote the variable to a closure:

static string GetVariableName<T>(Expression<Func<T>> expr)
{
    var body = (MemberExpression)expr.Body;

    return body.Member.Name;
}

You can use this method as follows:

static void Main()
{
    var someVar = 3;

    Console.Write(GetVariableName(() => someVar));
}

Note that this is pretty slow, so don’t use it in performance critical paths of your application. Every time this code runs, several objects are created (which causes GC pressure) and under the cover many non-inlinable methods are called and some heavy reflection is used.

For a more complete example, see here.

UPDATE

With C# 6.0, the nameof keyword is added to the language, which allows us to do the following:

static void Main()
{
    var someVar = 3;

    Console.Write(nameof(someVar));
}

This is obviously much more convenient and has the same cost has defining the string as constant string literal.