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Testing for Empty String

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21 Feb 2008CPOL 47K   12   17
A brief comparison of techniques of testing for empty strings

Background

Every once in a while, someone will post a snippet with code such as...

C#
if ( somestring == "" )

... and in many cases someone else will respond, "Always use if ( somestring.Length == 0 ), it's more efficient."

... or maybe someone will respond, "Always use if ( somestring == System.String.Empty ), it's more efficient."

And neither will back up his claim.

Here are some numbers; performing each test against a provided string (UInt32.MaxValue times) yields:

C:\>StrTest ""
00:01:09.3764731 // if ( providedstring == "" )
00:01:10.3869118 // if ( providedstring == localstaticemptystring )
00:01:10.1249723 // if ( providedstring == System.String.Empty )
00:00:38.1334581 // if ( providedstring.Length == 0 )

C:\>StrTest "abc"
00:01:36.3041617 // if ( providedstring == "" )
00:01:36.6285272 // if ( providedstring == localstaticemptystring )
00:01:35.9541459 // if ( providedstring == System.String.Empty )
00:00:31.6860051 // if ( providedstring.Length == 0 )

The difference between comparing against a literal empty string and a static empty string is negligible. And note that somehow when the provided string isn't empty, those tests take even longer!

Testing the Length of the string is the clear winner here, though it's not as Earth-shattering as some might have you believe.

History

  • 2008-02-21 First submitted

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Software Developer (Senior)
United States United States
BSCS 1992 Wentworth Institute of Technology

Originally from the Boston (MA) area. Lived in SoCal for a while. Now in the Phoenix (AZ) area.

OpenVMS enthusiast, ISO 8601 evangelist, photographer, opinionated SOB, acknowledged pedant and contrarian

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Comments and Discussions

 
GeneralHmm Pin
U-P-G-R-A-Y-E-D-D22-Feb-08 5:48
U-P-G-R-A-Y-E-D-D22-Feb-08 5:48 
GeneralRe: Hmm Pin
PIEBALDconsult22-Feb-08 7:48
mvePIEBALDconsult22-Feb-08 7:48 
QuestionHave you tested these? Pin
CCMint21-Feb-08 17:44
CCMint21-Feb-08 17:44 
AnswerRe: Have you tested these? Pin
PIEBALDconsult22-Feb-08 7:41
mvePIEBALDconsult22-Feb-08 7:41 
GeneralSo it is not me only... Pin
Oleg Shilo21-Feb-08 16:35
Oleg Shilo21-Feb-08 16:35 
Looks like another .NET myth...

I always preferred if (somestring == "")

Semantically "" and string.Empty work better than something.Length == 0 as they reflect the nature of you comparison. You see, you are not really interested in the length of the string, but rather in the string being empty.

"" arguebly better than string.Empty as it is less verbose.

Also keep in mind that if you even have "" 100 times in your code compiler creates static reference to the single string entry embedded in your assembly. Thus there is no any penalty for using "". And because of this "" is not different to localstaticemptystring but again "" is less verbose.

So I guess there is no real reason why "" should be avoided.

However semantics is a tricky topic and plenty of people would disagree with me.
GeneralRe: So it is not me only... Pin
PIEBALDconsult22-Feb-08 7:40
mvePIEBALDconsult22-Feb-08 7:40 
GeneralRe: So it is not me only... Pin
Oleg Shilo24-Feb-08 11:06
Oleg Shilo24-Feb-08 11:06 
GeneralRe: So it is not me only... Pin
Thomas Weller29-Nov-08 18:44
Thomas Weller29-Nov-08 18:44 
GeneralRe: So it is not me only... Pin
PIEBALDconsult30-Nov-08 5:57
mvePIEBALDconsult30-Nov-08 5:57 
GeneralRe: So it is not me only... Pin
Oleg Shilo30-Nov-08 12:10
Oleg Shilo30-Nov-08 12:10 
GeneralRe: So it is not me only... Pin
Thomas Weller30-Nov-08 23:34
Thomas Weller30-Nov-08 23:34 
GeneralRe: So it is not me only... Pin
PIEBALDconsult1-Dec-08 11:08
mvePIEBALDconsult1-Dec-08 11:08 
GeneralRe: So it is not me only... Pin
mm52850430-Jan-09 3:53
mm52850430-Jan-09 3:53 
GeneralRe: So it is not me only... Pin
PIEBALDconsult30-Jan-09 5:22
mvePIEBALDconsult30-Jan-09 5:22 
GeneralRe: So it is not me only... Pin
mm52850431-Jan-09 9:05
mm52850431-Jan-09 9:05 
GeneralRe: So it is not me only... Pin
PIEBALDconsult31-Jan-09 9:18
mvePIEBALDconsult31-Jan-09 9:18 
GeneralRe: So it is not me only... Pin
mm5285041-Feb-09 6:14
mm5285041-Feb-09 6:14 

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