C#

class A
{
    public Guid Guid;
    public A()
    {
        Guid = Guid.NewGuid();
    }
}

static void Main(string[] args)
{
    var a = new A();
    Console.WriteLine(a.Guid);
    Foo(a);
    Console.WriteLine(a.Guid);
}

static void Foo(A par)
{
    Console.WriteLine(par.Guid);
    par = new A();
    Console.WriteLine(par.Guid);
}

static void Main(string[] args)
{
    var a = new A();
    Console.WriteLine(a.Guid);
    Foo(ref a);
    Console.WriteLine(a.Guid);
}

static void Foo(ref A par)
{
    Console.WriteLine(par.Guid);
    par = new A();
    // btw, you still can do something like par.Guid = Guid.NewGuid();
    Console.WriteLine(par.Guid);
}

deep@Pune wrote:

then what is the use of ref and out keyword here???

arimao wrote:

cannot allow users to leave the application