Comments on: C# string.Empty vs “”

By: ASDF

ASDF — Mon, 23 Aug 2010 22:58:45 +0000

One interesting thing I observed when compiling with Visual studio.

If a variable is assigned with “” and not used in the code, then VS will throw warning.

If a variable is assigned with string.Empty and not used in the code, then VS will NOT throw warning.

I think “” is helpful to find out unused variables in the application

By: Random Links #9 | YASDW - yet another software developer weblog

Random Links #9 | YASDW - yet another software developer weblog — Mon, 13 Jul 2009 17:01:13 +0000

[...] C# string.Empty vs “” Interessant, weil ich (mich) das auch schon gefragt habe. Trotzdem ist eigentlich Wurst, Hauptsache konsistent im Projekt. [...]

By: Xander

Xander — Mon, 13 Jul 2009 13:10:48 +0000

@Lasse V. Karlsen
This is what i see from IL

empty quotes (“”) Test :
IL_001c: ldloc.0
IL_001d: ldstr “”
IL_0022: call bool [mscorlib]System.String::op_Equality(string,string)

string.Empty Test :
IL_001c: ldloc.0
IL_001d: ldsfld string [mscorlib]System.String::Empty
IL_0022: call bool [mscorlib]System.String::op_Equality(string,string)

As you can see there is a difference.
“” – represented as “ldstr” – pushes an object reference (type O) to a new string object

string.Empty – represented as “ldsfld” – pushes the value of a static field on the stack

By: Lasse V. Karlsen

Lasse V. Karlsen — Mon, 13 Jul 2009 11:51:47 +0000

Are you sure there is a difference except your runtime environment in that last test there?

Here’s the two comparisons, disassembled in release-mode:

if (TestValue == string.Empty)
00000036 mov edx,dword ptr ds:[022F102Ch]
0000003c mov ecx,dword ptr [ebp-10h]
0000003f call 75D95F98

if (TestValue == “”)
00000059 mov edx,dword ptr ds:[022F202Ch]
0000005f mov ecx,dword ptr [ebp-10h]
00000062 call 75D95F98

In debug mode there’s more code, but apart from the two constants in the first assembler line, there’s no difference. To me it looks like identical pieces of code.

What am I doing wrong?