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Shall I now always use String.Empty instead of ""In the past I always used "" everywhere for empty string in my code
without a problem. Now, do you think I should use String.Empty instead of "" (at all times) ? Let me know your thoughts. "anoni***@hotmail.com" wrote: If you're checking for an empty string it's better to use:> In the past I always used "" everywhere for empty string in my code > without a problem. > > Now, do you think I should use String.Empty instead of "" (at all > times) ? String.IsNullOrEmpty(strStringName) As of .NET 2.0 Hi,
There is very little difference between the two. "" is easy to write, easy to read, and near impossible to misunderstand.= = It will however create an object where String.Empty would not, but the "= " = object is reused throughout the lifespawn of your application so the = difference can therefore be ignored. Neither will detect a null string so if you can have null strings you ne= ed = to either check for that as well or use String.IsNullErEmtpy as Leon = pointed out. if(str =3D=3D null || str =3D=3D "") // or if(String.IsNullOrEmpty(str)) If, on the other hand, you know you will never get null strings, testing= = for String.Length =3D=3D 0 is the fastest way. On Thu, 23 Nov 2006 10:57:06 +0100, <anoni***@hotmail.com> wrote: > In the past I always used "" everywhere for empty string in my code -- => without a problem. > > Now, do you think I should use String.Empty instead of "" (at all > times) ? > > Let me know your thoughts. > Happy Coding! Morten Wennevik [C# MVP] Morten Wennevik wrote:
> "" is easy to write, easy to read, and near impossible to misunderstand. I was surprised to read that "" will create an object where> It will however create an object where String.Empty would not, but the "" > object is reused throughout the lifespawn of your application so the > difference can therefore be ignored. String.Empty will not - surely String.Empty is just a static field that points to an interned "" constant? Sure enough, Reflector shows that String.Empty is implemented as class string { static readonly string Empty = ""; } .... yet the below code shows that while both "" and String.Empty are interned, "" is not reference-equal to String.Empty. What gives? I thought the intern table was maintained across assembly boundaries, so it shouldn't matter that String.Empty comes from mscorlib.dll while "" comes from the app assembly. // using System; namespace StringEmptyTest { class Program { static void Main(string[] args) { Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); Console.WriteLine(String.IsInterned("") != null); Console.WriteLine(String.IsInterned(String.Empty) != null); Console.ReadLine(); } } } Hi Jon,
Your example code has been bothering me - it should work, however it doesn't and I can't figure out why :p But if you think that's weird, check out the following documentation I found on MSDN: "String.Intern Method" http://msdn2.microsoft.com/en-us/library/system.string.intern.aspx <quote> Version Considerations Starting with the .NET Framework version 2.0, there is a behavioral change in the Intern method. In the following C# code sequence, the variable str1 is assigned a reference to Empty, the variable str2 is assigned the reference to Empty that is returned by the Intern method, then the references contained in str1 and str2 are compared for equality. string str1 = String.Empty; string str2 = String.Intern(String.Empty); if ((object) str1) == ((object) str2) . In the .NET Framework version 1.1, str1 and str2 are not equal, but starting in the .NET Framework version 2.0, str1 and str2 are equal. </quote> Not in my test :| string str1 = String.Empty; string str2 = String.Intern(String.Empty); // false Console.WriteLine((object) str1 == (object) str2); // false Console.WriteLine((object) string.Empty == (object) ""); // true Console.WriteLine((object) "" == (object) ""); Using Reflector I verified that string.Empty is assigned the empty literal, "", in the class constructor (.cctor). I also verified, through testing, that interning works across assemblies; so I'm stumped here. The earliest version of the framework that I have installed on my machine is 2.0, verified in Add or Remove Programs. I also have 3.0 installed, if that makes a difference. Anyone know what's going on here? -- Show quoteDave Sexton "Jon Shemitz" <j**@midnightbeach.com> wrote in message news:4565F7B8.71B7A0BA@midnightbeach.com... > Morten Wennevik wrote: > >> "" is easy to write, easy to read, and near impossible to misunderstand. >> It will however create an object where String.Empty would not, but the "" >> object is reused throughout the lifespawn of your application so the >> difference can therefore be ignored. > > I was surprised to read that "" will create an object where > String.Empty will not - surely String.Empty is just a static field > that points to an interned "" constant? > > Sure enough, Reflector shows that String.Empty is implemented as > > class string > { > static readonly string Empty = ""; > } > > ... yet the below code shows that while both "" and String.Empty are > interned, "" is not reference-equal to String.Empty. What gives? I > thought the intern table was maintained across assembly boundaries, so > it shouldn't matter that String.Empty comes from mscorlib.dll while "" > comes from the app assembly. > > // > > using System; > > namespace StringEmptyTest > { > class Program > { > static void Main(string[] args) > { > Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); > Console.WriteLine(String.IsInterned("") != null); > Console.WriteLine(String.IsInterned(String.Empty) != null); > Console.ReadLine(); > } > } > } > > > -- > > .NET 2.0 for Delphi Programmers > www.midnightbeach.com/.net > What you need to know. Sorry to go OT -- for a monet -- but you're able to load documentation at
msdn2.microsoft.com? Quite a few people can not load pages at msdn2 for many weeks now and trying to figure out why. <%= Clinton Gallagher NET csgallagher AT metromilwaukee.com URL http://clintongallagher.metromilwaukee.com/ MAP http://wikimapia.org/#y=43038073&x=-88043838&z=17&l=0&m=h Show quote "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message news:%238GIy70EHHA.4024@TK2MSFTNGP04.phx.gbl... > Hi Jon, > > Your example code has been bothering me - it should work, however it > doesn't and I can't figure out why :p > > But if you think that's weird, check out the following documentation I > found on MSDN: > > "String.Intern Method" > http://msdn2.microsoft.com/en-us/library/system.string.intern.aspx > > <quote> > Version Considerations > Starting with the .NET Framework version 2.0, there is a behavioral change > in the Intern method. In the following C# code sequence, the variable str1 > is assigned a reference to Empty, the variable str2 is assigned the > reference to Empty that is returned by the Intern method, then the > references contained in str1 and str2 are compared for equality. > > string str1 = String.Empty; > string str2 = String.Intern(String.Empty); > if ((object) str1) == ((object) str2) . > > In the .NET Framework version 1.1, str1 and str2 are not equal, but > starting in the .NET Framework version 2.0, str1 and str2 are equal. > </quote> > > Not in my test :| > > string str1 = String.Empty; > string str2 = String.Intern(String.Empty); > > // false > Console.WriteLine((object) str1 == (object) str2); > > // false > Console.WriteLine((object) string.Empty == (object) ""); > > // true > Console.WriteLine((object) "" == (object) ""); > > > Using Reflector I verified that string.Empty is assigned the empty > literal, "", in the class constructor (.cctor). I also verified, through > testing, that interning works across assemblies; so I'm stumped here. > > The earliest version of the framework that I have installed on my machine > is 2.0, verified in Add or Remove Programs. I also have 3.0 installed, if > that makes a difference. > > Anyone know what's going on here? > > -- > Dave Sexton > > "Jon Shemitz" <j**@midnightbeach.com> wrote in message > news:4565F7B8.71B7A0BA@midnightbeach.com... >> Morten Wennevik wrote: >> >>> "" is easy to write, easy to read, and near impossible to misunderstand. >>> It will however create an object where String.Empty would not, but the >>> "" >>> object is reused throughout the lifespawn of your application so the >>> difference can therefore be ignored. >> >> I was surprised to read that "" will create an object where >> String.Empty will not - surely String.Empty is just a static field >> that points to an interned "" constant? >> >> Sure enough, Reflector shows that String.Empty is implemented as >> >> class string >> { >> static readonly string Empty = ""; >> } >> >> ... yet the below code shows that while both "" and String.Empty are >> interned, "" is not reference-equal to String.Empty. What gives? I >> thought the intern table was maintained across assembly boundaries, so >> it shouldn't matter that String.Empty comes from mscorlib.dll while "" >> comes from the app assembly. >> >> // >> >> using System; >> >> namespace StringEmptyTest >> { >> class Program >> { >> static void Main(string[] args) >> { >> Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); >> Console.WriteLine(String.IsInterned("") != null); >> Console.WriteLine(String.IsInterned(String.Empty) != null); >> Console.ReadLine(); >> } >> } >> } >> >> >> -- >> >> .NET 2.0 for Delphi Programmers >> www.midnightbeach.com/.net >> What you need to know. > > Hi,
I'm one of those people too - no secret here. It works most of the time for me, but it can be painfully slow or not load at all sometimes. I assume they are making some major modifications to the site. Although, msdn.microsoft.com/library and the search itself seem to work just fine, but once you click a search result that redirects you to msdn2, it's 20/80 ;) -- Show quoteDave Sexton "clintonG" <csgallag***@REMOVETHISTEXTmetromilwaukee.com> wrote in message news:urus1m1EHHA.4680@TK2MSFTNGP04.phx.gbl... > Sorry to go OT -- for a monet -- but you're able to load documentation at > msdn2.microsoft.com? > Quite a few people can not load pages at msdn2 for many weeks now and > trying to figure out why. > > <%= Clinton Gallagher > NET csgallagher AT metromilwaukee.com > URL http://clintongallagher.metromilwaukee.com/ > MAP http://wikimapia.org/#y=43038073&x=-88043838&z=17&l=0&m=h > > "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message > news:%238GIy70EHHA.4024@TK2MSFTNGP04.phx.gbl... >> Hi Jon, >> >> Your example code has been bothering me - it should work, however it >> doesn't and I can't figure out why :p >> >> But if you think that's weird, check out the following documentation I >> found on MSDN: >> >> "String.Intern Method" >> http://msdn2.microsoft.com/en-us/library/system.string.intern.aspx >> >> <quote> >> Version Considerations >> Starting with the .NET Framework version 2.0, there is a behavioral >> change in the Intern method. In the following C# code sequence, the >> variable str1 is assigned a reference to Empty, the variable str2 is >> assigned the reference to Empty that is returned by the Intern method, >> then the references contained in str1 and str2 are compared for equality. >> >> string str1 = String.Empty; >> string str2 = String.Intern(String.Empty); >> if ((object) str1) == ((object) str2) . >> >> In the .NET Framework version 1.1, str1 and str2 are not equal, but >> starting in the .NET Framework version 2.0, str1 and str2 are equal. >> </quote> >> >> Not in my test :| >> >> string str1 = String.Empty; >> string str2 = String.Intern(String.Empty); >> >> // false >> Console.WriteLine((object) str1 == (object) str2); >> >> // false >> Console.WriteLine((object) string.Empty == (object) ""); >> >> // true >> Console.WriteLine((object) "" == (object) ""); >> >> >> Using Reflector I verified that string.Empty is assigned the empty >> literal, "", in the class constructor (.cctor). I also verified, through >> testing, that interning works across assemblies; so I'm stumped here. >> >> The earliest version of the framework that I have installed on my machine >> is 2.0, verified in Add or Remove Programs. I also have 3.0 installed, >> if that makes a difference. >> >> Anyone know what's going on here? >> >> -- >> Dave Sexton >> >> "Jon Shemitz" <j**@midnightbeach.com> wrote in message >> news:4565F7B8.71B7A0BA@midnightbeach.com... >>> Morten Wennevik wrote: >>> >>>> "" is easy to write, easy to read, and near impossible to >>>> misunderstand. >>>> It will however create an object where String.Empty would not, but the >>>> "" >>>> object is reused throughout the lifespawn of your application so the >>>> difference can therefore be ignored. >>> >>> I was surprised to read that "" will create an object where >>> String.Empty will not - surely String.Empty is just a static field >>> that points to an interned "" constant? >>> >>> Sure enough, Reflector shows that String.Empty is implemented as >>> >>> class string >>> { >>> static readonly string Empty = ""; >>> } >>> >>> ... yet the below code shows that while both "" and String.Empty are >>> interned, "" is not reference-equal to String.Empty. What gives? I >>> thought the intern table was maintained across assembly boundaries, so >>> it shouldn't matter that String.Empty comes from mscorlib.dll while "" >>> comes from the app assembly. >>> >>> // >>> >>> using System; >>> >>> namespace StringEmptyTest >>> { >>> class Program >>> { >>> static void Main(string[] args) >>> { >>> Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); >>> Console.WriteLine(String.IsInterned("") != null); >>> Console.WriteLine(String.IsInterned(String.Empty) != null); >>> Console.ReadLine(); >>> } >>> } >>> } >>> >>> >>> -- >>> >>> .NET 2.0 for Delphi Programmers >>> www.midnightbeach.com/.net >>> What you need to know. >> >> > > Misery loves company ;-)
<%= Clinton Show quote "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message news:Ov4ii11EHHA.4740@TK2MSFTNGP03.phx.gbl... > Hi, > > I'm one of those people too - no secret here. > > It works most of the time for me, but it can be painfully slow or not load > at all sometimes. I assume they are making some major modifications to > the site. > > Although, msdn.microsoft.com/library and the search itself seem to work > just fine, but once you click a search result that redirects you to msdn2, > it's 20/80 ;) > > -- > Dave Sexton > > "clintonG" <csgallag***@REMOVETHISTEXTmetromilwaukee.com> wrote in message > news:urus1m1EHHA.4680@TK2MSFTNGP04.phx.gbl... >> Sorry to go OT -- for a monet -- but you're able to load documentation at >> msdn2.microsoft.com? >> Quite a few people can not load pages at msdn2 for many weeks now and >> trying to figure out why. >> >> <%= Clinton Gallagher >> NET csgallagher AT metromilwaukee.com >> URL http://clintongallagher.metromilwaukee.com/ >> MAP http://wikimapia.org/#y=43038073&x=-88043838&z=17&l=0&m=h >> >> "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message >> news:%238GIy70EHHA.4024@TK2MSFTNGP04.phx.gbl... >>> Hi Jon, >>> >>> Your example code has been bothering me - it should work, however it >>> doesn't and I can't figure out why :p >>> >>> But if you think that's weird, check out the following documentation I >>> found on MSDN: >>> >>> "String.Intern Method" >>> http://msdn2.microsoft.com/en-us/library/system.string.intern.aspx >>> >>> <quote> >>> Version Considerations >>> Starting with the .NET Framework version 2.0, there is a behavioral >>> change in the Intern method. In the following C# code sequence, the >>> variable str1 is assigned a reference to Empty, the variable str2 is >>> assigned the reference to Empty that is returned by the Intern method, >>> then the references contained in str1 and str2 are compared for >>> equality. >>> >>> string str1 = String.Empty; >>> string str2 = String.Intern(String.Empty); >>> if ((object) str1) == ((object) str2) . >>> >>> In the .NET Framework version 1.1, str1 and str2 are not equal, but >>> starting in the .NET Framework version 2.0, str1 and str2 are equal. >>> </quote> >>> >>> Not in my test :| >>> >>> string str1 = String.Empty; >>> string str2 = String.Intern(String.Empty); >>> >>> // false >>> Console.WriteLine((object) str1 == (object) str2); >>> >>> // false >>> Console.WriteLine((object) string.Empty == (object) ""); >>> >>> // true >>> Console.WriteLine((object) "" == (object) ""); >>> >>> >>> Using Reflector I verified that string.Empty is assigned the empty >>> literal, "", in the class constructor (.cctor). I also verified, >>> through testing, that interning works across assemblies; so I'm stumped >>> here. >>> >>> The earliest version of the framework that I have installed on my >>> machine is 2.0, verified in Add or Remove Programs. I also have 3.0 >>> installed, if that makes a difference. >>> >>> Anyone know what's going on here? >>> >>> -- >>> Dave Sexton >>> >>> "Jon Shemitz" <j**@midnightbeach.com> wrote in message >>> news:4565F7B8.71B7A0BA@midnightbeach.com... >>>> Morten Wennevik wrote: >>>> >>>>> "" is easy to write, easy to read, and near impossible to >>>>> misunderstand. >>>>> It will however create an object where String.Empty would not, but the >>>>> "" >>>>> object is reused throughout the lifespawn of your application so the >>>>> difference can therefore be ignored. >>>> >>>> I was surprised to read that "" will create an object where >>>> String.Empty will not - surely String.Empty is just a static field >>>> that points to an interned "" constant? >>>> >>>> Sure enough, Reflector shows that String.Empty is implemented as >>>> >>>> class string >>>> { >>>> static readonly string Empty = ""; >>>> } >>>> >>>> ... yet the below code shows that while both "" and String.Empty are >>>> interned, "" is not reference-equal to String.Empty. What gives? I >>>> thought the intern table was maintained across assembly boundaries, so >>>> it shouldn't matter that String.Empty comes from mscorlib.dll while "" >>>> comes from the app assembly. >>>> >>>> // >>>> >>>> using System; >>>> >>>> namespace StringEmptyTest >>>> { >>>> class Program >>>> { >>>> static void Main(string[] args) >>>> { >>>> Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); >>>> Console.WriteLine(String.IsInterned("") != null); >>>> Console.WriteLine(String.IsInterned(String.Empty) != null); >>>> Console.ReadLine(); >>>> } >>>> } >>>> } >>>> >>>> >>>> -- >>>> >>>> .NET 2.0 for Delphi Programmers >>>> www.midnightbeach.com/.net >>>> What you need to know. >>> >>> >> >> > > Hi Clinton,
:) Even stranger, FireFox appears to be slower than IE7 when loading msdn2 now (when it works :) -- Show quoteDave Sexton "clintonG" <csgallag***@REMOVETHISTEXTmetromilwaukee.com> wrote in message news:OW7fnUjFHHA.5000@TK2MSFTNGP03.phx.gbl... > Misery loves company ;-) > > <%= Clinton > > "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message > news:Ov4ii11EHHA.4740@TK2MSFTNGP03.phx.gbl... >> Hi, >> >> I'm one of those people too - no secret here. >> >> It works most of the time for me, but it can be painfully slow or not >> load at all sometimes. I assume they are making some major modifications >> to the site. >> >> Although, msdn.microsoft.com/library and the search itself seem to work >> just fine, but once you click a search result that redirects you to >> msdn2, it's 20/80 ;) >> >> -- >> Dave Sexton >> >> "clintonG" <csgallag***@REMOVETHISTEXTmetromilwaukee.com> wrote in >> message news:urus1m1EHHA.4680@TK2MSFTNGP04.phx.gbl... >>> Sorry to go OT -- for a monet -- but you're able to load documentation >>> at msdn2.microsoft.com? >>> Quite a few people can not load pages at msdn2 for many weeks now and >>> trying to figure out why. >>> >>> <%= Clinton Gallagher >>> NET csgallagher AT metromilwaukee.com >>> URL http://clintongallagher.metromilwaukee.com/ >>> MAP http://wikimapia.org/#y=43038073&x=-88043838&z=17&l=0&m=h >>> >>> "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message >>> news:%238GIy70EHHA.4024@TK2MSFTNGP04.phx.gbl... >>>> Hi Jon, >>>> >>>> Your example code has been bothering me - it should work, however it >>>> doesn't and I can't figure out why :p >>>> >>>> But if you think that's weird, check out the following documentation I >>>> found on MSDN: >>>> >>>> "String.Intern Method" >>>> http://msdn2.microsoft.com/en-us/library/system.string.intern.aspx >>>> >>>> <quote> >>>> Version Considerations >>>> Starting with the .NET Framework version 2.0, there is a behavioral >>>> change in the Intern method. In the following C# code sequence, the >>>> variable str1 is assigned a reference to Empty, the variable str2 is >>>> assigned the reference to Empty that is returned by the Intern method, >>>> then the references contained in str1 and str2 are compared for >>>> equality. >>>> >>>> string str1 = String.Empty; >>>> string str2 = String.Intern(String.Empty); >>>> if ((object) str1) == ((object) str2) . >>>> >>>> In the .NET Framework version 1.1, str1 and str2 are not equal, but >>>> starting in the .NET Framework version 2.0, str1 and str2 are equal. >>>> </quote> >>>> >>>> Not in my test :| >>>> >>>> string str1 = String.Empty; >>>> string str2 = String.Intern(String.Empty); >>>> >>>> // false >>>> Console.WriteLine((object) str1 == (object) str2); >>>> >>>> // false >>>> Console.WriteLine((object) string.Empty == (object) ""); >>>> >>>> // true >>>> Console.WriteLine((object) "" == (object) ""); >>>> >>>> >>>> Using Reflector I verified that string.Empty is assigned the empty >>>> literal, "", in the class constructor (.cctor). I also verified, >>>> through testing, that interning works across assemblies; so I'm stumped >>>> here. >>>> >>>> The earliest version of the framework that I have installed on my >>>> machine is 2.0, verified in Add or Remove Programs. I also have 3.0 >>>> installed, if that makes a difference. >>>> >>>> Anyone know what's going on here? >>>> >>>> -- >>>> Dave Sexton >>>> >>>> "Jon Shemitz" <j**@midnightbeach.com> wrote in message >>>> news:4565F7B8.71B7A0BA@midnightbeach.com... >>>>> Morten Wennevik wrote: >>>>> >>>>>> "" is easy to write, easy to read, and near impossible to >>>>>> misunderstand. >>>>>> It will however create an object where String.Empty would not, but >>>>>> the "" >>>>>> object is reused throughout the lifespawn of your application so the >>>>>> difference can therefore be ignored. >>>>> >>>>> I was surprised to read that "" will create an object where >>>>> String.Empty will not - surely String.Empty is just a static field >>>>> that points to an interned "" constant? >>>>> >>>>> Sure enough, Reflector shows that String.Empty is implemented as >>>>> >>>>> class string >>>>> { >>>>> static readonly string Empty = ""; >>>>> } >>>>> >>>>> ... yet the below code shows that while both "" and String.Empty are >>>>> interned, "" is not reference-equal to String.Empty. What gives? I >>>>> thought the intern table was maintained across assembly boundaries, so >>>>> it shouldn't matter that String.Empty comes from mscorlib.dll while "" >>>>> comes from the app assembly. >>>>> >>>>> // >>>>> >>>>> using System; >>>>> >>>>> namespace StringEmptyTest >>>>> { >>>>> class Program >>>>> { >>>>> static void Main(string[] args) >>>>> { >>>>> Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); >>>>> Console.WriteLine(String.IsInterned("") != null); >>>>> Console.WriteLine(String.IsInterned(String.Empty) != null); >>>>> Console.ReadLine(); >>>>> } >>>>> } >>>>> } >>>>> >>>>> >>>>> -- >>>>> >>>>> .NET 2.0 for Delphi Programmers >>>>> www.midnightbeach.com/.net >>>>> What you need to know. >>>> >>>> >>> >>> >> >> > > I urge you to respond to my recent news article posted in several Microsoft
newsgroups related to MSDN and ASP.NET development. The subject is "For Microsoft Partners and Customers Who Can't Download or Access MSDN2..." Take your own stance of course but please let your voice be heard about these server failures. <%= Clinton Gallagher NET csgallagher AT metromilwaukee.com URL http://clintongallagher.metromilwaukee.com/ MAP http://wikimapia.org/#y=43038073&x=-88043838&z=17&l=0&m=h Show quote "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message news:um8cijjFHHA.5004@TK2MSFTNGP03.phx.gbl... > Hi Clinton, > > :) > > Even stranger, FireFox appears to be slower than IE7 when loading msdn2 > now (when it works :) > > -- > Dave Sexton > > "clintonG" <csgallag***@REMOVETHISTEXTmetromilwaukee.com> wrote in message > news:OW7fnUjFHHA.5000@TK2MSFTNGP03.phx.gbl... >> Misery loves company ;-) >> >> <%= Clinton >> >> "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message >> news:Ov4ii11EHHA.4740@TK2MSFTNGP03.phx.gbl... >>> Hi, >>> >>> I'm one of those people too - no secret here. >>> >>> It works most of the time for me, but it can be painfully slow or not >>> load at all sometimes. I assume they are making some major >>> modifications to the site. >>> >>> Although, msdn.microsoft.com/library and the search itself seem to work >>> just fine, but once you click a search result that redirects you to >>> msdn2, it's 20/80 ;) >>> >>> -- >>> Dave Sexton >>> >>> "clintonG" <csgallag***@REMOVETHISTEXTmetromilwaukee.com> wrote in >>> message news:urus1m1EHHA.4680@TK2MSFTNGP04.phx.gbl... >>>> Sorry to go OT -- for a monet -- but you're able to load documentation >>>> at msdn2.microsoft.com? >>>> Quite a few people can not load pages at msdn2 for many weeks now and >>>> trying to figure out why. >>>> >>>> <%= Clinton Gallagher >>>> NET csgallagher AT metromilwaukee.com >>>> URL http://clintongallagher.metromilwaukee.com/ >>>> MAP http://wikimapia.org/#y=43038073&x=-88043838&z=17&l=0&m=h >>>> >>>> "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message >>>> news:%238GIy70EHHA.4024@TK2MSFTNGP04.phx.gbl... >>>>> Hi Jon, >>>>> >>>>> Your example code has been bothering me - it should work, however it >>>>> doesn't and I can't figure out why :p >>>>> >>>>> But if you think that's weird, check out the following documentation I >>>>> found on MSDN: >>>>> >>>>> "String.Intern Method" >>>>> http://msdn2.microsoft.com/en-us/library/system.string.intern.aspx >>>>> >>>>> <quote> >>>>> Version Considerations >>>>> Starting with the .NET Framework version 2.0, there is a behavioral >>>>> change in the Intern method. In the following C# code sequence, the >>>>> variable str1 is assigned a reference to Empty, the variable str2 is >>>>> assigned the reference to Empty that is returned by the Intern method, >>>>> then the references contained in str1 and str2 are compared for >>>>> equality. >>>>> >>>>> string str1 = String.Empty; >>>>> string str2 = String.Intern(String.Empty); >>>>> if ((object) str1) == ((object) str2) . >>>>> >>>>> In the .NET Framework version 1.1, str1 and str2 are not equal, but >>>>> starting in the .NET Framework version 2.0, str1 and str2 are equal. >>>>> </quote> >>>>> >>>>> Not in my test :| >>>>> >>>>> string str1 = String.Empty; >>>>> string str2 = String.Intern(String.Empty); >>>>> >>>>> // false >>>>> Console.WriteLine((object) str1 == (object) str2); >>>>> >>>>> // false >>>>> Console.WriteLine((object) string.Empty == (object) ""); >>>>> >>>>> // true >>>>> Console.WriteLine((object) "" == (object) ""); >>>>> >>>>> >>>>> Using Reflector I verified that string.Empty is assigned the empty >>>>> literal, "", in the class constructor (.cctor). I also verified, >>>>> through testing, that interning works across assemblies; so I'm >>>>> stumped here. >>>>> >>>>> The earliest version of the framework that I have installed on my >>>>> machine is 2.0, verified in Add or Remove Programs. I also have 3.0 >>>>> installed, if that makes a difference. >>>>> >>>>> Anyone know what's going on here? >>>>> >>>>> -- >>>>> Dave Sexton >>>>> >>>>> "Jon Shemitz" <j**@midnightbeach.com> wrote in message >>>>> news:4565F7B8.71B7A0BA@midnightbeach.com... >>>>>> Morten Wennevik wrote: >>>>>> >>>>>>> "" is easy to write, easy to read, and near impossible to >>>>>>> misunderstand. >>>>>>> It will however create an object where String.Empty would not, but >>>>>>> the "" >>>>>>> object is reused throughout the lifespawn of your application so the >>>>>>> difference can therefore be ignored. >>>>>> >>>>>> I was surprised to read that "" will create an object where >>>>>> String.Empty will not - surely String.Empty is just a static field >>>>>> that points to an interned "" constant? >>>>>> >>>>>> Sure enough, Reflector shows that String.Empty is implemented as >>>>>> >>>>>> class string >>>>>> { >>>>>> static readonly string Empty = ""; >>>>>> } >>>>>> >>>>>> ... yet the below code shows that while both "" and String.Empty are >>>>>> interned, "" is not reference-equal to String.Empty. What gives? I >>>>>> thought the intern table was maintained across assembly boundaries, >>>>>> so >>>>>> it shouldn't matter that String.Empty comes from mscorlib.dll while >>>>>> "" >>>>>> comes from the app assembly. >>>>>> >>>>>> // >>>>>> >>>>>> using System; >>>>>> >>>>>> namespace StringEmptyTest >>>>>> { >>>>>> class Program >>>>>> { >>>>>> static void Main(string[] args) >>>>>> { >>>>>> Console.WriteLine(Object.ReferenceEquals(String.Empty, "")); >>>>>> Console.WriteLine(String.IsInterned("") != null); >>>>>> Console.WriteLine(String.IsInterned(String.Empty) != null); >>>>>> Console.ReadLine(); >>>>>> } >>>>>> } >>>>>> } >>>>>> >>>>>> >>>>>> -- >>>>>> >>>>>> .NET 2.0 for Delphi Programmers >>>>>> www.midnightbeach.com/.net >>>>>> What you need to know. >>>>> >>>>> >>>> >>>> >>> >>> >> >> > > <anoni***@hotmail.com> wrote:
> In the past I always used "" everywhere for empty string in my code Which do you find easier to read? That's pretty much the only > without a problem. > > Now, do you think I should use String.Empty instead of "" (at all > times) ? difference of any significance, IMO. -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too And what happens if string interning is disabled? Doesn't this mean that
each time you have a "" in your code that you will have the overhead of allocating memory on the heap and creating a new string object? Gabriel Show quote "Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message news:MPG.1fd006413738da3298d655@msnews.microsoft.com... > <anoni***@hotmail.com> wrote: >> In the past I always used "" everywhere for empty string in my code >> without a problem. >> >> Now, do you think I should use String.Empty instead of "" (at all >> times) ? > > Which do you find easier to read? That's pretty much the only > difference of any significance, IMO. > > -- > Jon Skeet - <sk***@pobox.com> > http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet > If replying to the group, please do not mail me too Gabriel Lozano-Morán <ab***@frontbridge.com> wrote:
> And what happens if string interning is disabled? Doesn't this mean that String interning isn't something you can enable or disable, as far as > each time you have a "" in your code that you will have the overhead of > allocating memory on the heap and creating a new string object? I'm aware - and at that point, the C# language specification is being violated. I don't alter my programming style in order to suit situations like that - it's like changing your style to suit a situation where garbage collection doesn't occur. -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too See:
http://msdn2.microsoft.com/en-us/library/system.runtime.compilerservices.compilationrelaxationsattribute.aspx http://msdn2.microsoft.com/en-us/library/system.runtime.compilerservices.compilationrelaxations.aspx Gabriel Lozano-Morán "Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message Gabriel Lozano-Morán <ab***@frontbridge.com> wrote:news:MPG.1fd5f739350795f798d66e@msnews.microsoft.com... > And what happens if string interning is disabled? Doesn't this mean that String interning isn't something you can enable or disable, as far as> each time you have a "" in your code that you will have the overhead of > allocating memory on the heap and creating a new string object? I'm aware - and at that point, the C# language specification is being violated. I don't alter my programming style in order to suit situations like that - it's like changing your style to suit a situation where garbage collection doesn't occur. -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too Gabriel Lozano-Morán <ab***@frontbridge.com> wrote:
> See: How bizarre. Using that would certainly mean you were no longer using a > http://msdn2.microsoft.com/en-us/library/system.runtime.compilerservi > ces.compilationrelaxationsattribute.aspx language which conformed to the C# language spec. However, you would have to *explicitly* use that attribute, so again I can't see that it's actually a consideration to think about in normal coding. -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too >How bizarre. Using that would certainly mean you were no longer using a Actually the C# 2.0 compiler adds this attribute to all assemblies,>language which conformed to the C# language spec. However, you would >have to *explicitly* use that attribute unless you explicitly specify otherwise. Which part of the spec do you mean this would violate? I know that previous compiler versions sometimes relied on interning to implement the switch statement for strings, but that doesn't seem to be the case anymore. Mattias -- Mattias Sjögren [C# MVP] mattias @ mvps.org http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com Please reply only to the newsgroup. Mattias Sjögren <mattias.dont.want.spam@mvps.org> wrote:
> >How bizarre. Using that would certainly mean you were no longer using a Yikes - you're right. Interesting that it doesn't seem to have the > >language which conformed to the C# language spec. However, you would > >have to *explicitly* use that attribute > > Actually the C# 2.0 compiler adds this attribute to all assemblies, > unless you explicitly specify otherwise. indicated effect. Here's a sample program: using System; using System.Diagnostics; class Test1 { public static string Empty = ""; } class Test2 { public static string Empty = ""; } class Test { static void Main() { string s1 = Test1.Empty; string s2 = Test2.Empty; Console.WriteLine (object.ReferenceEquals(s1, s2)); } } That prints "True" on my box, which will only be true if the strings are interned. Printing string.IsInterned("x") shows that being interned too. Odd. I'm intrigued now... > Which part of the spec do you mean this would violate? I know that From > previous compiler versions sometimes relied on interning to implement > the switch statement for strings, but that doesn't seem to be the case > anymore. http://www.jaggersoft.com/csharp_standard/9.4.4.5.htm#string-literal <quote> Each string literal does not necessarily result in a new string instance. When two or more string literals that are equivalent according to the string equality operator (§14.9.7), appear in the same assembly, these string literals refer to the same string instance. </quote> (I'll have to look at how strings are switched now, too. So much to look at, so little time...) -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too Hi Jon,
Apparently, CompilationRelaxations.NoStringInterning only disables string interning for the NGEN utility. This setting is automatically applied on all assemblies compiled by the C# 2.0 compiler, as Mattias already mentioned, and as you've pointed out Interning is certainly not disabled in 2.0 :) The documentation Gabriel has cited is definitely misleading and should be updated. I don't believe that C# or .NET provides the ability to disable string interning in code. "Starting with the .NET Framework version 2.0, you can override the use of the intern pool when you use the Native Image Generator (Ngen.exe) to install an assembly to the native image cache on a local computer. For more information, see Performance Considerations in the Remarks section for the Intern property." (and by "property" I think they mean "method" :) "String.IsInterned Method" http://msdn2.microsoft.com/en-us/library/system.string.isinterned.aspx "The .NET Framework version 2.0 introduces the CompilationRelaxations.NoStringInterning enumeration member. The NoStringInterning member marks an assembly as not requiring string-literal interning. You can apply NoStringInterning to an assembly using the CompilationRelaxationsAttribute attribute. When you use the Native Image Generator (Ngen.exe) to install that assembly to the native image cache on the local computer, string interning is not used." "String.Intern Method" http://msdn2.microsoft.com/en-us/library/system.string.intern(vs.80).aspx -- Dave Sexton "Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message Mattias Sjögren <mattias.dont.want.spam@mvps.org> wrote:news:MPG.1fd6d4262968b8f098d677@msnews.microsoft.com... > >How bizarre. Using that would certainly mean you were no longer using a Yikes - you're right. Interesting that it doesn't seem to have the> >language which conformed to the C# language spec. However, you would > >have to *explicitly* use that attribute > > Actually the C# 2.0 compiler adds this attribute to all assemblies, > unless you explicitly specify otherwise. indicated effect. Here's a sample program: using System; using System.Diagnostics; class Test1 { public static string Empty = ""; } class Test2 { public static string Empty = ""; } class Test { static void Main() { string s1 = Test1.Empty; string s2 = Test2.Empty; Console.WriteLine (object.ReferenceEquals(s1, s2)); } } That prints "True" on my box, which will only be true if the strings are interned. Printing string.IsInterned("x") shows that being interned too. Odd. I'm intrigued now... > Which part of the spec do you mean this would violate? I know that From> previous compiler versions sometimes relied on interning to implement > the switch statement for strings, but that doesn't seem to be the case > anymore. http://www.jaggersoft.com/csharp_standard/9.4.4.5.htm#string-literal <quote> Each string literal does not necessarily result in a new string instance. When two or more string literals that are equivalent according to the string equality operator (§14.9.7), appear in the same assembly, these string literals refer to the same string instance. </quote> (I'll have to look at how strings are switched now, too. So much to look at, so little time...) -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too Correct at the moment it is only for NGEN-ed assemblies but if I am not
mistaken it is possible that in future versions it will be possible to disable the intern pool imho that's the reason why the documentation might seem misleading. Personally I have never understand the need for string interning and the overhead that comes with it because how many times will you have two or more exact string literals? Gabriel Show quote "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message news:urSCZS0EHHA.5028@TK2MSFTNGP03.phx.gbl... > Hi Jon, > > Apparently, CompilationRelaxations.NoStringInterning only disables string > interning for the NGEN utility. This setting is automatically applied on > all assemblies compiled by the C# 2.0 compiler, as Mattias already > mentioned, and as you've pointed out Interning is certainly not disabled > in 2.0 :) > > The documentation Gabriel has cited is definitely misleading and should be > updated. I don't believe that C# or .NET provides the ability to disable > string interning in code. > > "Starting with the .NET Framework version 2.0, you can override the use of > the intern pool when you use the Native Image Generator (Ngen.exe) to > install an assembly to the native image cache on a local computer. For > more information, see Performance Considerations in the Remarks section > for the Intern property." (and by "property" I think they mean "method" > :) > > "String.IsInterned Method" > http://msdn2.microsoft.com/en-us/library/system.string.isinterned.aspx > > "The .NET Framework version 2.0 introduces the > CompilationRelaxations.NoStringInterning enumeration member. The > NoStringInterning member marks an assembly as not requiring string-literal > interning. You can apply NoStringInterning to an assembly using the > CompilationRelaxationsAttribute attribute. When you use the Native Image > Generator (Ngen.exe) to install that assembly to the native image cache on > the local computer, string interning is not used." > > "String.Intern Method" > http://msdn2.microsoft.com/en-us/library/system.string.intern(vs.80).aspx > > -- > Dave Sexton > > "Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message > news:MPG.1fd6d4262968b8f098d677@msnews.microsoft.com... > Mattias Sjögren <mattias.dont.want.spam@mvps.org> wrote: >> >How bizarre. Using that would certainly mean you were no longer using a >> >language which conformed to the C# language spec. However, you would >> >have to *explicitly* use that attribute >> >> Actually the C# 2.0 compiler adds this attribute to all assemblies, >> unless you explicitly specify otherwise. > > Yikes - you're right. Interesting that it doesn't seem to have the > indicated effect. Here's a sample program: > > using System; > using System.Diagnostics; > > class Test1 > { > public static string Empty = ""; > } > > class Test2 > { > public static string Empty = ""; > } > > class Test > { > static void Main() > { > string s1 = Test1.Empty; > string s2 = Test2.Empty; > Console.WriteLine (object.ReferenceEquals(s1, s2)); > } > } > > That prints "True" on my box, which will only be true if the strings > are interned. Printing string.IsInterned("x") shows that being interned > too. > > Odd. I'm intrigued now... > >> Which part of the spec do you mean this would violate? I know that >> previous compiler versions sometimes relied on interning to implement >> the switch statement for strings, but that doesn't seem to be the case >> anymore. > > From > http://www.jaggersoft.com/csharp_standard/9.4.4.5.htm#string-literal > > <quote> > Each string literal does not necessarily result in a new string > instance. When two or more string literals that are equivalent > according to the string equality operator (§14.9.7), appear in the same > assembly, these string literals refer to the same string instance. > </quote> > > (I'll have to look at how strings are switched now, too. So much to > look at, so little time...) > > -- > Jon Skeet - <sk***@pobox.com> > http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet > If replying to the group, please do not mail me too > "Gabriel Lozano-Morán" wrote: Depends on how much HTML/XML you're generating, I guess.> > Correct at the moment it is only for NGEN-ed assemblies but if I am not > mistaken it is possible that in future versions it will be possible to > disable the intern pool imho that's the reason why the documentation might > seem misleading. Personally I have never understand the need for string > interning and the overhead that comes with it because how many times will > you have two or more exact string literals? "Mattias Sjögren" wrote: That's news to me, but a quick test shows that you're right.> Actually the C# 2.0 compiler adds this attribute to all assemblies, > unless you explicitly specify otherwise. > > Which part of the spec do you mean this would violate? I know that > previous compiler versions sometimes relied on interning to implement > the switch statement for strings, but that doesn't seem to be the case > anymore. That's rather strange - I wonder if they found that the cost of interning switch input strings was greater than the savings from using ReferenceEquals instead of Equals (when comparing the input string to the case tags). "Jon Skeet [C# MVP]" <sk***@pobox.com> wrote You can't disable it. At least not that I was able to find, and I looked for > > And what happens if string interning is disabled? > String interning isn't something you can enable or disable, as far as > I'm aware - and at that point, the C# language specification is being > violated. quite a while. I wrote up a blog entry on my findings with string interning and when / where it can save memory (at least in the case i'm worried about): http://www.coversant.com/dotnetnuke/Default.aspx?tabid=88&EntryID=24 <anoni***@hotmail.com> wrote:
> In the past I always used "" everywhere for empty string in my code From the Blog at:> without a problem. > > Now, do you think I should use String.Empty instead of "" (at all > times) ? http://blogs.msdn.com/brada/archive/2003/04/22/49997.aspx > "" actually creates an object, it will likely be So there ya have it. String.Empty is obviously a zillion times better than > 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. "". :) In all honesty though, I don't think it ever really matters. Certainly not in any cases I've ever come across. I use string.empty, because I dislike the look of "". Hi,
I use string.Empty because that's what everyone I talked to had told me since the original framework beta. Personally, I don't really care either way now, but it's just a habit. If I could shake the OCD involved I might be able to start using "" instead, which seems cleaner to me ;) -- Show quoteDave Sexton <anoni***@hotmail.com> wrote in message news:1164275826.495190.9500@j72g2000cwa.googlegroups.com... > In the past I always used "" everywhere for empty string in my code > without a problem. > > Now, do you think I should use String.Empty instead of "" (at all > times) ? > > Let me know your thoughts. > I personally prefer string.Empty over "" in code. It is just a matter of
flavor but it can be a good thing to make it a guideline whether or not you to use "" vs string.Empty for the team. Gabriel Lozano-Morán Show quote "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message news:ex1125yEHHA.3820@TK2MSFTNGP02.phx.gbl... > Hi, > > I use string.Empty because that's what everyone I talked to had told me > since the original framework beta. > > Personally, I don't really care either way now, but it's just a habit. > > If I could shake the OCD involved I might be able to start using "" > instead, which seems cleaner to me ;) > > -- > Dave Sexton > > <anoni***@hotmail.com> wrote in message > news:1164275826.495190.9500@j72g2000cwa.googlegroups.com... >> In the past I always used "" everywhere for empty string in my code >> without a problem. >> >> Now, do you think I should use String.Empty instead of "" (at all >> times) ? >> >> Let me know your thoughts. >> > > Hi Gabriel,
I don't think I'd be too concerned if different team members used "" or string.Empty. I'd leave that up to personal preference. It really isn't that important, IMO. -- Show quoteDave Sexton "Gabriel Lozano-Morán" <ab***@frontbridge.com> wrote in message news:unF1JQzEHHA.3436@TK2MSFTNGP03.phx.gbl... >I personally prefer string.Empty over "" in code. It is just a matter of >flavor but it can be a good thing to make it a guideline whether or not you >to use "" vs string.Empty for the team. > > Gabriel Lozano-Morán > > "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message > news:ex1125yEHHA.3820@TK2MSFTNGP02.phx.gbl... >> Hi, >> >> I use string.Empty because that's what everyone I talked to had told me >> since the original framework beta. >> >> Personally, I don't really care either way now, but it's just a habit. >> >> If I could shake the OCD involved I might be able to start using "" >> instead, which seems cleaner to me ;) >> >> -- >> Dave Sexton >> >> <anoni***@hotmail.com> wrote in message >> news:1164275826.495190.9500@j72g2000cwa.googlegroups.com... >>> In the past I always used "" everywhere for empty string in my code >>> without a problem. >>> >>> Now, do you think I should use String.Empty instead of "" (at all >>> times) ? >>> >>> Let me know your thoughts. >>> >> >> > > Like I said, whatever gets you off. It is like starting with a the letter
"p" for all your method arguments. Some do it and some don't. Gabriel Show quote "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message news:uAjOxYzEHHA.2104@TK2MSFTNGP03.phx.gbl... > Hi Gabriel, > > I don't think I'd be too concerned if different team members used "" or > string.Empty. I'd leave that up to personal preference. It really isn't > that important, IMO. > > -- > Dave Sexton > > "Gabriel Lozano-Morán" <ab***@frontbridge.com> wrote in message > news:unF1JQzEHHA.3436@TK2MSFTNGP03.phx.gbl... >>I personally prefer string.Empty over "" in code. It is just a matter of >>flavor but it can be a good thing to make it a guideline whether or not >>you to use "" vs string.Empty for the team. >> >> Gabriel Lozano-Morán >> >> "Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message >> news:ex1125yEHHA.3820@TK2MSFTNGP02.phx.gbl... >>> Hi, >>> >>> I use string.Empty because that's what everyone I talked to had told me >>> since the original framework beta. >>> >>> Personally, I don't really care either way now, but it's just a habit. >>> >>> If I could shake the OCD involved I might be able to start using "" >>> instead, which seems cleaner to me ;) >>> >>> -- >>> Dave Sexton >>> >>> <anoni***@hotmail.com> wrote in message >>> news:1164275826.495190.9500@j72g2000cwa.googlegroups.com... >>>> In the past I always used "" everywhere for empty string in my code >>>> without a problem. >>>> >>>> Now, do you think I should use String.Empty instead of "" (at all >>>> times) ? >>>> >>>> Let me know your thoughts. >>>> >>> >>> >> >> > >  
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