(C#) pass by reference clarification? HELP! (Quick question)

When you call a method in C#, the default is to pass by value: a copy is made of the value and that it passed to the method to work with.
Nothing the method does to the variable will affect the outside world:

public void NoAffect(int x)
   {
   Console.WriteLine(x)
   x = 0;
   Console.WriteLine(x)
   }
...
   int myVar = 666;
   NoAffect(myVar);
   Console.WriteLine(myVar);

Will give you:

666
0
666

Because a copy of the myVar variable was made and passed the NoAffect.
This means that you can call NoAffect with a variable or a constant value:

...
   int myVar = 666;
   NoAffect(myVar);
   Console.WriteLine(myVar);
...
   NoAffect(666);
   Console.WriteLine(666);

Will give you the same results.

That is the same regardless of whether the datatype passed is a Value type or a Reference type:

public class MyClass
   {
   public int x;
   }

public void NoAffect(MyClass mc)
   {
   Console.WriteLine(mc.x)
   mc = new MyClass{x = 0};
   Console.WriteLine(mc.x)
   }
...
   MyClass myVar = new MyClass {x = 666};
   NoAffect(myVar);
   Console.WriteLine(myVar.x);

And it will print the same thing:

666
0
666

Because the reference was copied and passed to the method.

OK so far?

When you pass by reference that doesn't happen: a copy isn't passed, but an alias is - the variable in the method is the variable outside it:

public void Affect(ref int x)
   {
   Console.WriteLine(x)
   x = 0;
   Console.WriteLine(x)
   }
...
   int myVar = 666;
   Affect(myVar);
   Console.WriteLine(ref myVar);

Will give you:

666
0
0

Again, the same thing happens with Reference types:

...
		MyClass mc = new MyClass {x = 666};
		Affect (ref mc);
		Console.WriteLine(mc.x);
...
public void Affect(ref MyClass mc)
   {
   Console.WriteLine(mc.x);
   mc = new MyClass{x = 0};
   Console.WriteLine(mc.x);
   }

Because an alias to the reference variable is passed this time.

This means that Affect cannot be called with a constant value at all - you can't pass an alias to a constant, it must be what is called an L-Value: something that can be on the "left hand side" of an assignment operator.

Technically, a reference is passed (even to a value type) but it shouldn't be confused with the "reference" in "reference type" because it's not the same thing - passing a genuine reference to a Value type variable would require boxing and unboxing and that doesn't happen with pass by reference - which is why I called it an alias above. so I'd disagree (and agree!) with both the descriptions in your question!

Does that seem a little clearer?