In C#, should I use string.Empty or String.Empty or “”?

Basically,

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 

The best code is no code at all and consequently, less code is better code.

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 "".

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

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 the C#...shortcut if you will. Same as with Int32 and int. As far as "", nor 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.

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

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.

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.

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.

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.

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 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.

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.

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 ;-)

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.