“ref” keyword and reference types [duplicate]

Answer 1

Let

class A
{
    public string Blah { get; set; }
}

void Do (ref A a)
{
    a = new A { Blah = "Bar" };
}

then

A a = new A { Blah = "Foo" };
Console.WriteLine(a.Blah); // Foo
Do (ref a);
Console.WriteLine(a.Blah); // Bar

---

But if just

void Do (A a)
{
    a = new A { Blah = "Bar" };
}

then

A a = new A { Blah = "Foo" };
Console.WriteLine(a.Blah); // Foo
Do (a);
Console.WriteLine(a.Blah); // Foo