I am certain that string.Empty is more efficient than using "" in .Net languages. What I would like to know is WHY is it more efficient?
+2
A:
I don't think there is any performance gain in using string.Empty over "".
Its just a matter of personal preference.
rahul
2009-12-11 11:27:53
Agree, but `string.Empty` is definitely more explicit than ""
klausbyskov
2009-12-11 11:29:11
Stylecop recommends using string.Empty, surely this is not just because it is more visually appealing than ""?
JL
2009-12-11 11:29:48
Sebastian - incorrect. If "" is in code, then all references to "" will be interned to the same instance, just like any other string constant
thecoop
2009-12-11 11:32:14
Agreed that this is wrong
SpoBo
2009-12-11 11:32:37
the coop is right, sebastian is wrong.
Rob Fonseca-Ensor
2009-12-11 11:36:35
+2
A:
string.Empty is a singleton static const string that has been constructed, but "" will create a new string that is empty.
Benny
2009-12-11 11:28:18
...which also means that it's interned - there's only one copy of the string in memory regardless of how many times it's used.
ctford
2009-12-11 11:30:17
It won't create a new instance every time you reference "", it will use a reference to the single interned value of ""
thecoop
2009-12-11 11:33:01
wrong, look up string interning. If you use: `new string("")` however, you'll use more memory...
Rob Fonseca-Ensor
2009-12-11 11:35:59
If you use `new string("")` you'll get a compile-time error - there isn't a string constructor taking just a string.
Jon Skeet
2009-12-11 11:49:12
+12
A:
I think in most cases there is no difference. In normal cases, when you use "" in your code this string will be interned and the same string instance will be reused. So there will not be more string instances around when using "" as compared to String.Empty.
If you want proof:
Dim a As String
Dim b As String
a = ""
b = ""
Console.WriteLine(Object.ReferenceEquals(a, b)) ' Prints True '
The above code prints True also if you replace one of them with String.Empty, so you can even mix the approaches without creating extra string instances.
Bottom line: the difference is personal taste.
Fredrik Mörk
2009-12-11 11:30:24
Is there any overhead accessing an interned string compared to accessing a puplic static string?
JonoW
2009-12-11 11:38:14
Ok, accepted answer. This is good to know, because a lot of IT geeks frown upon the use of "". I guess this is another StyleCop rule worth ignoring too.
JL
2009-12-11 11:38:45
@JonoW: never measured it, but it would surprise me if there is any difference.
Fredrik Mörk
2009-12-11 11:40:16
+4
A:
First of all, I'm not sure that it is more efficient. A reason it is a static is, it is basically a constant: there is only one empty string.
A more important issue is that there are some inconsistencies with string interning in .NET, which can result in comparisons with String.empty not always returning the expected result, depending on what version of the runtime you're using. Eric Lippert has written a fascinating blog post about it here.
(Example taken from Eric's post)
object obj = "";
string str1 = "";
string str2 = String.Empty;
Console.WriteLine(obj == str1); // true
Console.WriteLine(str1 == str2); // true
Console.WriteLine(obj == str2); // sometimes true, sometimes false?!
Rik
2009-12-11 11:31:11
A:
"" will create an instance of an empty string in your application. Sure, .NET interns the string constants, but still, you will create one instance. String.Empty, on the other hand, does not create any instance.
Konamiman
2009-12-11 11:34:53
+1
A:
If you fancy reading some assembler based evidence of this the following post could be interesting: http://stackoverflow.com/questions/263191/in-c-should-i-use-string-empty-or-string-empty-or/1588678#1588678
Actually, there are some interesting answers in that whole thread.
Joe
2009-12-11 11:37:34
+1
A:
Pre 2.0, it was correct that String.Empty is more efficient, but ever since there is no difference. See http://stackoverflow.com/questions/151472/what-is-the-difference-between-string-empty-and/151481#151481
nd
2009-12-11 11:40:43