Reputation: 12395

In C#, should I use string.Empty or String.Empty or "" to intitialize a string?

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;

string willi = String.Empty;

string willi = "";

or what?

Upvotes: 813

Answers (30)

l33t

Reputation: 19937

Fact

"" does NOT equal ""

It's been 16 years, and none of the answers pinpoint this very fact. I encourage you to always use string.Empty since the developer can then be 100% certain that the value is indeed an empty string.

Proof

internal class Program
{
    static void Main(string[] args)
    {
        Foo(string.Empty);
        Foo("");
        Foo("");
    }

    private static void Foo(string s) => Console.WriteLine(s.Length);
}

Output:

0
0
7

.NET Fiddle here.

So what's going on here?

Well, there are many Unicode letters which are hard - sometimes impossible - to see. Here I used a Zero Width Space and successfully fooled you that you got an empty string. If you would use my "empty string" in production code, you may very well get an exception later on.

Upvotes: 0

Steve

Reputation: 216273

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.

SOME YEARS AFTER
Microsoft has retired the https://connect .microsoft.com website so the discussion there is no more available. However there is this article https://learn.microsoft.com/en-us/dotnet/csharp/misc/cs0219 with an interesting remark that seems to confirm the previous reasons:

The compiler generates this warning only when the variable value is a compile-time constant. Assigning a non-constant expression or method result to a local variable makes it easier to observe those expressions in the debugger. It also makes the result reachable, preventing garbage collection while that variable is reachable.

Upvotes: 18

user34577

Reputation: 93

While difference is very, VERY little, the difference still exists.

"" creates an 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.
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.

Upvotes: 3

RhinoTX

Reputation: 169

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.

Upvotes: 4

RBT

Reputation: 25877

I performed a simple test using following method in a .NET v4.5 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 suggests that all three variables namely str1, str2 and str3 though being initialized using different syntax are pointing to the same string (of zero length) object in memory .

So internally they have no difference. And it all boils down to convenience of which one you or your team wants to use. This behavior of string class is known as string interning in .NET Framework. Eric Lippert has a very nice blog here describing this concept.

Upvotes: 15

Keith Howard

Reputation: 387

Possibly a controversial comment, but, generally, I find that my life is easier when I act consistently with Microsoft. We can't possibly know the full deeply embedded reasons (sometimes highly rigorous, and sometime kludgy, I imagine) for why they do things.

They use "" in automatically generated files like the Assembly file, so that is what I do. In fact, when I try to replace any below "" with String.Empty, Visual Studio crashes on me. There is probably a logical explanation for this, but with my limited knowledge, if I just do what they do, most of the time, things work out. (Contra: I am aware they some automatically generated files also use String.Empty, which kind of shatters my point. :) )

<Assembly: System.Reflection.AssemblyCulture("")>
<Assembly: System.Reflection.AssemblyDescription("")>
<Assembly: System.Reflection.AssemblyFileVersion("1.0.0.0")>
<Assembly: System.Reflection.AssemblyKeyFile("")>
<Assembly: System.Reflection.AssemblyProduct("")>
<Assembly: System.Reflection.AssemblyTitle("")>

Upvotes: 0

Mentoliptus

Reputation: 2985

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

Upvotes: 62

Wouter

Reputation: 2938

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.)

Upvotes: 1

Andrew

Reputation: 144

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.

Upvotes: 5

Silviu Niculita

Reputation: 177

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.

Upvotes: 15

5argon

Reputation: 3863

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.

Upvotes: 2

Remotec

Reputation: 10758

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

(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.

Upvotes: 3

aBetterGamer

Reputation: 5289

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.

C# Code

private void Test1()
{
    string test1 = string.Empty;    
    string test11 = test1;
}

private void Test2()
{
    string test2 = "";    
    string test22 = test2;
}

IL Code

.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

Assembly code

        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

Upvotes: 403

Konrad Rudolph

Reputation: 545518

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.

Upvotes: 92

Dimitry

Reputation: 71

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.

Upvotes: 7

Jon Skeet

Reputation: 1499950

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.

Upvotes: 899

Jimmy

Reputation: 91432

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 "".

Upvotes: 49

sergiol

Reputation: 4335

On http://blogs.msdn.com/b/brada/archive/2003/04/22/49997.aspx :

As David implies, there difference between String.Empty and "" 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... while String.Empty creates no object... so if you are really looking for ultimately in memory efficiency, I suggest String.Empty. However, you should keep in mind the difference is so trival you will like never see it in your code...
As for System.String.Empty or string.Empty or String.Empty... my care level is low ;-)

Upvotes: 1

mckamey

Reputation: 17529

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.

Upvotes: 5

Jason Baker

Reputation: 198547

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.

Upvotes: 11

Wayne Murphy

Reputation:

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.

Upvotes: 7

John Rudy

Reputation: 37850

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.

Upvotes: 24

tvanfosson

Reputation: 532435

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.

Upvotes: 4

Calanus

Reputation: 26267

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.

Upvotes: 4

zendar

Reputation: 13562

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

Upvotes: 8

CasperTDK

Reputation:

I doesn't make a difference. The last one is the quickest to type though :)

Upvotes: 5

Magus

Reputation: 577

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.

Upvotes: 1