"ref" keyword and reference types

Question

someone in my team stumbled upon a peculiar use of the ref keyword on a reference type

class A { /* ... */ } 

class B
{    
    public void DoSomething(ref A myObject)
    {
       // ...
    }
}

Is there any reason someone sane would do such a thing? I can't find a use for this in C#

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