Menu
I've read some article about String.Empty vs "" and I also do test by my self. Different between them are below.
String.Empty
L_0001: ldsfld string [mscorlib]System.String::Empty
""
L_0001: ldstr ""
After I talk with my friends they argue that String.Empty is faster than "" because under the hood (at assembly level) ldstr do more 1 circle than ldsfld. (I can't remember steps that make them different)
I want to know how can I check about this aspect of performance.
526
The ldstr instruction pushes an object reference (type O ) to a new string object representing the specific string literal stored in the metadata.
Empty will serve you better than using “”. In the cases where String. Empty will not work either because of the code evaluation OR because of the performance considerations, yes, use “” instead. But, do it because there is a supportable reason, not because you think it may produce faster code.
Using equals Method This technique can be used to check the emptiness of String as well. All you need to do is to call equals() method on empty String literal and pass the object you are testing as shown below : String nullString = null; String empty = new String(); boolean test = "". equals(empty); // true System.
The ldsfld operation pushes the value of a static field onto the evaluation stack, while the ldstr pushes a reference to a meta data string literal.
The performance difference (if any) would be minimal. Newer versions of the compiler actually substitutes "" for String.Empty.
You should also consider the readability and maintainability of the code. Using String.Empty it's clearer that you actually mean an empty string and not just forgot to type something in the string literal.
I took a look at the native code created.
C# 3, release mode, x86:
string a = String.Empty;
0000002a mov eax,dword ptr ds:[0356102Ch]
0000002f mov dword ptr [ebp-8],eax
string b = "";
00000032 mov eax,dword ptr ds:[0356202Ch]
00000038 mov dword ptr [ebp-0Ch],eax
C# 3, release mode, x64:
string a = String.Empty;
0000003b mov rax,12711050h
00000045 mov rax,qword ptr [rax]
00000048 mov qword ptr [rsp+28h],rax
string b = "";
0000004d mov rax,12713048h
00000057 mov rax,qword ptr [rax]
0000005a mov qword ptr [rsp+30h],rax
So, in the end the code is identical.
166
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
