Accessing private member of a parameter within a Static method?

How can this code compile? The code below in the operator int CAN access a private variable of the class MyValue? Why?

class Program
{
    static void Main(string[] args)
    {
        Myvalue my = new Myvalue(100);
        Console.WriteLine(my + 100);
        Console.Read();
    }
}


public class Myvalue
{
    private int _myvalue;

    public Myvalue(int value)
    {
        _myvalue = value;
    }

    public static implicit operator int(Myvalue v)
    {
        return v._myvalue;
    }
}