In C#, I want to initialize a string value with an empty string.
How should I do this? What is the right way, and why?
string willi = string.Empty;
or
string willi = String.Empty;
or
string willi = "";
or what?
Use whatever you and your team find the most readable.
Other answers have suggested that a new string is created every time you use "". This is not true - due to string interning, it will be created either once per assembly or once per AppDomain (or possibly once for the whole process - not sure on that front). This difference is negligible - massively, massively insignificant.
Which you find more readable is a different matter, however. It's subjective and will vary from person to person - so I suggest you find out what most people on your team like, and all go with that for consistency. Personally I find "" easier to read.
The argument that "" and " " are easily mistaken for each other doesn't really wash with me. Unless you're using a proportional font (and I haven't worked with any developers who do) it's pretty easy to tell the difference.
string.Empty is not a constant. That means that in a number of cases where a compile-time constant is required, string.Empty isn't even legal. This includes case "" blocks in switch statements, default values of optional parameters, parameters and properties in applying attributes, and a lot of other situations (left to the reader). So given that string.Empty is disallowed in some common situations, it is better to use the ""-everywhere convention. - Jeppe Stig Nielsen
There really is no difference from a performance and code generated standpoint. In performance testing, they went back and forth between which one was faster vs the other, and only by milliseconds.
In looking at the behind the scenes code, you really don't see any difference either. The only difference is in the IL, which string.Empty use the opcode ldsfld
and "" uses the opcode ldstr, but that is only because string.Empty is static, and both instructions do the same thing.
If you look at the assembly that is produced, it is exactly the same.
private void Test1()
{
string test1 = string.Empty;
string test11 = test1;
}
private void Test2()
{
string test2 = "";
string test22 = test2;
}
.method private hidebysig instance void
Test1() cil managed
{
// Code size 10 (0xa)
.maxstack 1
.locals init ([0] string test1,
[1] string test11)
IL_0000: nop
IL_0001: ldsfld string [mscorlib]System.String::Empty
IL_0006: stloc.0
IL_0007: ldloc.0
IL_0008: stloc.1
IL_0009: ret
} // end of method Form1::Test1
.method private hidebysig instance void
Test2() cil managed
{
// Code size 10 (0xa)
.maxstack 1
.locals init ([0] string test2,
[1] string test22)
IL_0000: nop
IL_0001: ldstr ""
IL_0006: stloc.0
IL_0007: ldloc.0
IL_0008: stloc.1
IL_0009: ret
} // end of method Form1::Test2
string test1 = string.Empty;
0000003a mov eax,dword ptr ds:[022A102Ch]
0000003f mov dword ptr [ebp-40h],eax
string test11 = test1;
00000042 mov eax,dword ptr [ebp-40h]
00000045 mov dword ptr [ebp-44h],eax
string test2 = "";
0000003a mov eax,dword ptr ds:[022A202Ch]
00000040 mov dword ptr [ebp-40h],eax
string test22 = test2;
00000043 mov eax,dword ptr [ebp-40h]
00000046 mov dword ptr [ebp-44h],eax
The best code is no code at all:
The fundamental nature of coding is that our task, as programmers, is to recognize that every decision we make is a trade-off. […] Start with brevity. Increase the other dimensions as required by testing.
Consequently, less code is better code: Prefer "" to string.Empty or String.Empty. Those two are six times longer with no added benefit — certainly no added clarity, as they express the exact same information.
i is better than a long variable name. Even more general, shorter variable names that convey the same information, in the same clarity, are always preferable. It’s just that to express the necessary information you need a certain character length, and I’m not denying this (nobody is). - Konrad Rudolph
One difference is that if you use a switch-case syntax, you can't write case string.Empty: because it's not a constant. You get a Compilation error : A constant value is expected
Look at this link for more info: string-empty-versus-empty-quotes
switch statement is one very good example. Also, if you make an optional parameter, like void MyMethod(string optional = "") { ... }, it's also not possible to use string.Empty. And then of course if you want to define a const field or local variable, const string myString = ""; the again "" is the only option. If only string.Empty were a constant field, there wouldn't be a difference. But it's not, so in some cases you have to use "". So why not use "" all the time? - Jeppe Stig Nielsenstring.Empty prevents you from attaining consistency in your code base: you must use two different entities to express the same thing. And to add to the list of things you can't do: you can't use string.Empty with attributes. - Pragmateek
I'd prefer string to String. choosing string.Empty over "" is a matter of choosing one and sticking with it. Advantage of using string.Empty is it is very obvious what you mean, and you don't accidentally copy over non-printable characters like "\x003" in your "".
"" is dangerous when copy/pasting is void, I claim, because you never copy/paste the empty string. For other strings, it is always something to be mindful of, of course. - Timo
I wasn't going to chime in, but I'm seeing some wrong info getting tossed out here.
I, personally, prefer string.Empty. That's a personal preference, and I bend to the will of whatever team I work with on a case-by-case basis.
As some others have mentioned, there is no difference at all between string.Empty and String.Empty.
Additionally, and this is a little known fact, using "" is perfectly acceptable. Every instance of "" will, in other environments, create an object. However, .NET interns its strings, so future instances will pull the same immutable string from the intern pool, and any performance hit will be negligible. Source: Brad Abrams.
I personally prefer "" unless there is a good reason to something more complex.
String.Empty and string.Empty are equivalent. String is the BCL class name; string is its C# alias (or shortcut, if you will). Same as with Int32 and int. See the docs for more examples.
As far as "" is concerned, I'm not really sure.
Personally, I always use string.Empty.
Just about every developer out there will know what "" means. I personally encountered String.Empty the first time and had to spend some time searching google to figure out if they really are the exact same thing.
string.Empty? Did you know what "" was the first time you saw it? - David R Tribble
This topic is pretty old and long, so excuse me if this behavior has been mentioned somewhere else. (And point me to the answer that covers this)
I have found a difference in the behavior of the compiler if you use string.Empty or double quotes. The difference shows itself if you don't use the string variable initialized with string.Empty or with double quotes.
In case of initialization with string.Empty then the Compiler Warning
CS0219 - The variable 'x' is assigned but its value is never used
is never emitted while in case of initialization with double quotes you get the expected message.
This behavior is explained in the Connect article at this link: https://connect.microsoft.com/VisualStudio/feedback/details/799810/c-warning-cs0219-not-reported-when-assign-non-constant-value
Basically, if I get it right, they want to allow a programmer to set a variable with the return value of a function for debugging purposes without bothering him with a warning message and thus they limited the warning only in case of costant assignments and string.Empty is not a constant but a field.
var unused = "literal"; can be completely optimized away (removed) by the compiler. It can have no side effects. On the other hand, var unused = MyClass.Member; cannot be removed entirely. That is because reading Member could have side effects. If Member is a static property with a get accessor, it is clear that the call to the getter must be kept. But even if Member is a static field, there may be the side effect that the static constructor may run. Sure it would be bad coding style to have it that way. But you need a dummy to read Member. - Jeppe Stig Nielsen
I performed this very simple test using following function in a console application:
private static void CompareStringConstants()
{
string str1 = "";
string str2 = string.Empty;
string str3 = String.Empty;
Console.WriteLine(object.ReferenceEquals(str1, str2)); //prints True
Console.WriteLine(object.ReferenceEquals(str2, str3)); //prints True
}
This clearly suggests that all three variables namely str1, str2 and str3 though being initialized using different syntax but are pointing to the exactly same string (of zero length) object in memory . I performed this test in .Net 4.5 console application. So internally they have no difference and it all boils down to convenience of which one you want to use as a programmer. This behavior of string class is known as string interning in .Net. Eric Lippert has a very nice blog here describing this concept.
Any of the above.
There are many, many better things to pontificate. Such as what colour bark suits a tree best, I think vague brown with tinges of dulcet moss.
I strongly prefer String.Empty, aside from the other reasons to ensure you know what it is and that you have not accidentally removed the contents, but primarily for internationalization. If I see a string in quotes then I always have to wonder whether that is new code and it should be put into a string table. So every time code gets changed/reviewed you need to look for "something in quotes" and yes you can filter out the empty strings but I tell people it is good practice to never put strings in quotes unless you know it won't get localized.
No one mentioned that in VisualStudio String is color coded differently then string. Which is important for readability. Also, lower case is usually used for vars and type, not a big deal but String.Empty is a constant and not a var or type.
I doesn't make a difference. The last one is the quickest to type though :)
string is synonym for System.String type, They are identical.
Values are also identical: string.Empty == String.Empty == ""
I would not use character constant "" in code, rather string.Empty or String.Empty - easier to see what programmer meant.
Between string and String I like lower case string more just because I used to work with Delphi for lot of years and Delphi style is lowercase string.
So, if I was your boss, you would be writing string.Empty
It doesn't matter - they are exactly the same thing. However, the main thing is that you must be consistent
p.s. I struggle with this sort of "whats the right thing" all the time.
I use the third, but of the other two the first seems less odd. string is an alias for String, but seeing them across an assignment feels off.
Either of the first two would be acceptable to me. I would avoid the last one because it is relatively easy to introduce a bug by putting a space between the quotes. This particular bug would be difficult to find by observation. Assuming no typos, all are semantically equivalent.
[EDIT]
Also, you might want to always use either string or String for consistency, but that's just me.
It is totally a code-style preference, do to how .NET handles strings. However, here are my opinions :)
I always use the BCL Type names when accessing static methods, properties and fields: String.Empty or Int32.TryParse(...) or Double.Epsilon
I always use the C# keywords when declaring new instances: int i = 0; or string foo = "bar";
I rarely use undeclared string literals as I like to be able to scan the code to combine them into reusable named constants. The compiler replaces constants with the literals anyway so this is more of a way to avoid magic strings/numbers and to give a little more meaning to them with a name. Plus changing the values is easier.
I have personally witnessed "" resulting in (minor) problems twice. Once was due to a mistake of a junior developer new to team-based programming, and the other was a simple typo, but the fact is using string.Empty would have avoided both issues.
Yes, this is very much a judgement call, but when a language gives you multiple ways to do things, I tend to lean toward the one that has the most compiler oversight and strongest compile-time enforcement. That is not "". It's all about expressing specific intent.
If you type string.EMpty or Strng.Empty, the compiler lets you know you did it wrong. Immediately. It simply will not compile. As a developer you are citing specific intent that the compiler (or another developer) cannot in any way misinterpret, and when you do it wrong, you can't create a bug.
If you type " " when you mean "" or vice-versa, the compiler happily does what you told it to do. Another developer may or may not be able to glean your specific intent. Bug created.
Long before string.Empty was a thing I've used a standard library that defined the EMPTY_STRING constant. We still use that constant in case statements where string.Empty is not allowed.
Whenever possible, put the compiler to work for you, and eliminate the possibility of human error, no matter how small. IMO, this trumps "readability" as others have cited.
Specificity and compile time enforcement. It's what's for dinner.
I would favor string.Empty over String.Empty because you can use it without needing to include a using System; in your file.
As for the picking "" over string.Empty, it is personal preference and should be decided by your team.
string.Empty constant without importing using System namespace - Keywords in C# simply get converted to their fully qualified name which includes the namespace as well before being written as MSIL in the output *.dll or *.exe file. So effectively string.Empty gets written as System.String.Empty in the MSIL by the compiler. And as you already might be knowing that if you mention fully qualified type name then you can give a skip to importing namespaces at the top of your code file. - RBT
The compiler should make them all the same in the long run. Pick a standard so that your code will be easy to read, and stick with it.
I was just looking at some code and this question popped into my mind which I had read some time before. This is certainly a question of readability.
Consider the following C# code...
(customer == null) ? "" : customer.Name
vs
(customer == null) ? string.empty : customer.Name
I personally find the latter less ambiguous and easier to read.
As pointed out by others the actual differences are negligible.
I use "" because it will be colored distinctively yellow in my code... for some reason String.Empty is all white in my Visual Studio Code theme. And I believe that matters to me the most.
I think the second is "proper," but to be honest I don't think it will matter. The compiler should be smart enough to compile any of those to the exact same bytecode. I use "" myself.
On http://blogs.msdn.com/b/brada/archive/2003/04/22/49997.aspx :
As David implies, there difference between
String.Emptyand""are pretty small, but there is a difference.""actually creates an object, it will likely be pulled out of the string intern pool, but still... whileString.Emptycreates no object... so if you are really looking for ultimately in memory efficiency, I suggestString.Empty. However, you should keep in mind the difference is so trival you will like never see it in your code...
As forSystem.String.Emptyorstring.EmptyorString.Empty... my care level is low ;-)
The empty string is like empty set just a name that everybody uses to call "". Also in formal languages strings created from an alphabet that have zero length are called the empty string. Both set and string have a special symbol for it. Empty string: ε and empty set: ∅. If you want to talk about this zero length string you will call it the empty string so everybody knows exactly what you are referring to. Now in case you name it the empty string why not use string.Empty in code, its shows the intention is explicit. Downside is that it’s not a constant and therefore not available everywhere, like in attributes. (It's not a constant for some technical reasons, see the reference source.)
While difference is very, VERY little, the difference still exist.
1) "" creates object while String.Empty does not. But this object will be created once and will be referenced from the string pool later if you have another "" in the code.
2) String and string are the same, but I would recommend to use String.Empty (as well as String.Format, String.Copy etc.) since dot notation indicates class, not operator, and having class starting with capital letter conforms to C# coding standards.