Recently a colleague at work told me not to use
Empty are very different, and I don't suggest arbitrarily switching between them. But neither has any extra "cost", since
Empty is a single fixed reference (you can use it any number of times).
There is no "pollution" on the stack caused by a ldsfld - that concern is.... crazy. Loading a
null is arguably marginally cheaper, but could cause null-reference exceptions if you aren't careful about checking the value.
Personally, I use neither... If I want an empty string I use
"" - simple and obvious. Interning means this also has no per-usage overhead.
At the IL level, the difference here between "" and Empty is just ldstr vs ldsfld - but both give the same single interned string reference. Furthermore, in more recent .NET versions the JIT has direct interception of these, yielding the empty string reference without actually doing a static field lookup. Basically, there is exactly no reason to care either way, except readability. I just use "".