Cannot use String.Empty as a default value for an optional parameter in C# - then what's the point?

Question

I am reading Effective C# by Bill Wagner. In Item 14 - Minimize Duplicate Initialization Logic, he shows the following example of using the new optional parameters feature in a constructor:

public MyClass(int initialCount = 0, string name = "")

Notice that he used "" instead of string.Empty.
He comments:

You'll note [in an example above] that the second constructor specified "" for the default value on the name parameter, rather than the more customary string.Empty. That's because string.Empty is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter.

If we cannot use the string.Empty static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.

UPDATE
Just a follow up comment. According to MSDN:

Each optional parameter has a default value as part of its definition. If no argument is sent for that parameter, the default value is used. Default values must be constants.

Then we aren't be able to use System.Environment.NewLine either, or use newly instantiated objects as default values. I haven't used VS2010 yet, and this is disappointing!

Answer 1

I never use string.Empty, I can't see the point of it. Maybe it makes it easier for people that are really new to programming, but I doubt it's useful even for that.

Answer 2

I think the idea behind string.Empty is it enhances readability. It is not like newline where there is any difference between how it is represented on different platforms. It's ashame it can't be used in a default parameter. However, it will not cause any issues if you port between Windows and something like Mono on Linux.

Answer 3

As of the C# 2.0 compiler, there is very little point to String.Empty anyway, and in fact in many cases it's a pessimisation, since the compiler can inline some references to "" but can't do the same with String.Empty.

In C# 1.1 it was useful to avoid creating lots of independent objects all containing the empty string, but those days are gone. "" works just fine.