Where is ASP.NET 3.5 on IIS ?

Most people on installing .NET 3.5 on the server "expect" an entry for  v3.5 under the ASP.NET version Tab in IIS manager. And not finding that entry start panicking. If you have been one of those read on. The more tech savvy folks try to run aspnet_regiis -i from the v3.5 framework folder... but even that is missing πŸ™‚


That brings us to the question

What exactly is ASP.NET 3.5 ?

Take a look at the v3.5 framework folder you will not find most of the files needed for ASP.NET to run like aspnet_isapi.dll / aspnet_filter.dll / aspnet_regiis.exe / aspnet_regsql.exe...

The reason being .NET 3.5 is not a stand alone framework like v2.0 or v1.1 . It is just an extension of the 2.0 framework. The extension provides developers with new language features like Anonymous Types, Extension Methods, Lambda Expressions and of course LINQ .... and AJAX is now integrated ... also you have a few new ASP.NET controls <asp:ListView>, <asp:LinqDataSource>, <asp:DataPager>

Will I get ASP.NET version 3.5 under the ASP.NET tab in IIS 6.0 ?

Nope. Because as far as IIS is concerned nothing has changed. The aspnet_isapi.dll from the version 2.0 folder will still handle the requests and there is no new ISAPI dll specific to version 3.5. So you don't have to change any Script Mappings in IIS ...just leave the web application pointing to v2.0 under the ASP.NET Tab. And this brings us to the next question

What exactly is the extension ?

For that if you have Visual Studio 2008 go ahead and create a Website targeting the .NET 3.5 framework. Then go to the Property Pages of the Website and select References. You will find an entry like this


And those four assembly references provide the new features of v3.5.  Here is a 10,000 ft view of the functionality implemented in these assemblies

System.Core - Provides namespaces like System.Linq, System.IO

System.Data.DataSetExtensions - LINQ to DataSet

System.Web.Extensions - AJAX

System.Xml.Linq - New XML API.. supports LINQ to XML

Do I have to configure anything manually ?

No. When you install the .NET 3.5 redistributable on the server it installs these assemblies in the GAC. And any website that refers to these assemblies can fetch them from the GAC so you do not have to configure anything manually. All you need to do is publish the content to a web application that is marked with ASP.NET v2.0

And now you should be thinking

The new language features should require a new compiler. How exactly is the new compiler used ?

The answer is your web.config file. When you create an ASP.NET 3.5 website in Visual Studio 2008 an entry is made in the web.config something like

    <compiler language="c#;cs;csharp" extension=".cs" warningLevel="4"
              type="Microsoft.CSharp.CSharpCodeProvider, System, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <providerOption name="CompilerVersion" value="v3.5"/>
      <providerOption name="WarnAsError" value="false"/>

The new features do require a new compiler to be used and the web.config tells .NET that the v3.5 compiler has to be used.

What about IIS 7.0 ?

IIS 7.0 is no different. 


[UPDATE 2012] Where is ASP.NET 4.5 …wait Where is .NET 4.5 ?

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Comments (125)

  1. Hosam Kamel says:

    Most people on installing .NET 3.5 on the server "expect" an entry for v3.5 under the ASP.NET version

  2. Phil Baldwin says:

    Thank you for this – it has solved this problem for me – I had already gone down the blind alley with aspnet_regiis.

    It is much appreciated, especially with the detail of the reasons why this happens.

    Thanks again.

  3. Wonderful article and great explanation.

    Thanks Vijayshinva Karnure

  4. Very good article indeed.

    I have to admit it is irritating not being able to set the version in IIS.  Maybe/hopefully as I begin using the new updates I will start to understand better then reasoning Microsoft had for doing this.  Right now the only reason I can think of is making the upgrade a smaller install.

  5. sunillkc says:

    Simple and very good explanation

  6. Very good article. I was also one of those looking for a way to "register" ASP.NET 3.5 in IIS.

  7. chuck123q says:

    If I am using MSBuildToolsPath set to 3.5 is their anyway to find the path to tools I need (aspnet_regiis) from within msbuild?

  8. Sheree says:

    Thanks for laying out all of the answers in one article!

  9. News says:

    Most people on installing .NET 3.5 on the server &quot;expect&quot; an entry for v3.5 under the ASP.NET

  10. gc says:

    Thank you for this info, it was very helpful. Clear consice and accurate.

  11. Nguyễn Gia Thăng says:

    ASP.NET Version when you  installing .NET 3.5 ?

  12. Richard says:

    thanks..this article was very helpful

  13. Manoj Nair says:

    Thanks a lot… Saved me a lot of unnecessary work

  14. Kamil says:

    A related issue — my computer does not have an ASPNET account. How do I create it? I have just now installed v3.5 of .NET framework on Windows 2003 Server.


  15. kyma says:

    A really good article to explain something actually quite fundamental.  A lot of developers are not aware of the basic concept that 3.5 is not a standalone framework.

    Thank you.

  16. Loretta says:

    Great article.  Saved me some time!

  17. YTC says:

    Exactly what I was looking for.

    Thank you!!!

  18. Parveen Battan says:

    Thanks for such a nice article

  19. David Anderson says:

    Very helpful!!  Like you started your article – I was one of those confused by the whole thing.  Not any more!

  20. Thanks, a very helpful article!

  21. Huseyin says:

    Thank you for that clarification.

  22. Tanmoy Ghosh says:

    Great! thanks for this extremely helpful information

  23. sangam says:

    yes, useful.i had iis installed after .ne t 3.5 and i

    wished asp.net  3.5 extension in iis dropdownlist.

    but it is clear now.




  24. Mahesh says:

    Really a good Article!!!!!!!!!!!!!!!!!!1

  25. Sylvie says:

    Thank you for clarifying how 3.5 is working in this article. I just installed 2008 and converted the 1st projects. I was confused when I saw 2.0 references in IIS ….  Your article really helped me.

  26. Saroj says:

    I’ve an Web Application in ASP.NET 3.5, I’m trying to run it through IIS 6.0, how ever the application is not running. After 10 mins its showing Timeout error waiting for a program to execute. The command being executed was "C:WINDOWS….v3.5……vbc.exe" /noconfig @"C:WINDOWS………v2.0.50727………… *.cmdline"

    PLease suggest something, its very urgent.

  27. Levi says:

    Boy do I feel silly  πŸ™‚  

    This was great info, thanks!

  28. udayt says:

    Thanks Buddy!

    Very helpful.

  29. Balat says:

    I re-installed version 3.5 twice… I thought there is a problem… thanks for this article… now I can smile πŸ™‚

  30. Vinayy says:

    I was also one of those looking for a way to "register" ASP.NET 3.5 in IIS.

    I share my view with Federico Caldas (his post dated 10 Apr 2008).

  31. praveen says:

    Excellent I was Looking for the same thing.

    Thanks a lot for such a good explination.

  32. Rainer says:

    Excellent article! Exactly the information I was looking for. Thanks  Danke!

  33. David says:

    Brilliant. Excellent and very useful article.

    Thanks a lot for sharing your knowledge.

  34. tc says:

    This is a very nice article. Thank you very much.

  35. I don’t know how many times I get asked this same question daily. Thank you for writing the article so clearly and simply. I will certainly offer your URL as part of my answer in the future.

  36. Thanxs a lot!

    Jus to be clear this is the same for IIS 5.0, 5.1, 6.0 and 7.0 ?

    From your explanations its seems to be that it is

  37. very helpful says:

    Very helpful and very clear explanation. Great

  38. Jonathan K. Herschel says:

    Thanks, you saved me from pulling ALL of my hair out.

  39. Prema says:

    Very helpful and informative article.

  40. Nirav Shah says:

    I have created one project on Visual studio 2005.  I craeted virtual directory and it worked fine. I was able to access it. Now I have installed Visual studio 2008. I have upgraded my project to 2008. I also created virtual directory.

                 This time it is giving an error when I am trying to browse my project from I.E. The error is failed to access iis metabase. Can you please help me regarding this?

  41. matt says:

    Thanks! I just installed VS2008 and was hella confused about "registering" 3.5

  42. dikasths says:

    Kalo arthro. Kerdizeis ena xryso papari .NET 3.5

  43. CM Cody says:

    Simple, clean, and direct explanation.  Excellent article. Much appreciated.

  44. Sam says:

    Excellent Article. I was confused about .net 3.5.

    Thanks a lot

  45. Senthil says:

    Hats Off !!!!!!

    Thanks a Bunch !

  46. Ben says:

    Thanks! Of course, MS could maybe make this a little more obvious?

  47. mauri says:

    excelent post!!! really helpful

  48. Vern says:

    Great info and to the point. Bravo!

  49. Priya says:

    Excellent Article. Answer to many questions. Thanks

  50. Abhas says:

    Thanks for the very Informative article

  51. sun says:

    good info and nice presentation..thx

  52. Most people on installing .NET 3.5 on the server &quot;expect&quot; an entry for&#160; v3.5 under the

  53. NicMartel says:

    Bastards!!  I spent an enormous amount of time trying to resolve this obvious issue.  It SHOULD BE MENTIONNED CLEARLY UP-FRONT BY MICROSOFT ON THE DOWNLOAD PAGE…  f idiots!!  The proof is above… see how many have wasted valuable time!!!  and think of HOW MANY have not stumbled ONTO THIS ARTICLE!!!!!! 1000s…. again f idiots!

  54. ashwinkavale says:

    Excellent Article…solved my confusion regarding  3.5 and IIS.

  55. ashwinkavale says:

    Excellent Article…resolved my confusion regarding  3.5 and IIS.

  56. Mr Farney says:

    Thank!  This article was very helpful.

  57. neevan says:

    thanks …

    very useful …………..

  58. Jini says:

    Well explained…. simple and neat

  59. Tyler says:

    Thanks, was looking for 3.5 in the tab.  

  60. pallavi says:

    thanks buddy it really helps us to know new things for 3.5

  61. Thanks – I was scratching my head when I first installed 3.5 I like most others was expecting the entry in Iss to change which framework was being used.

  62. Brian B says:

    Extremely helpful and well written (with nice illustrations)

  63. Faraz says:

    Thanks for the article…I was looking for the entry, this really saved me a lot of time.

  64. Nishantha says:

    Excellent… simple, brief and lets you know what you need to know..

  65. Hara Prasad says:

    Excellent and useful article. Earlier I was thinking 3.5 as a standalone appln, but now its clear to me. I got this article while searching for article regarding the migration of project from .net 2.0 to .net 3.5. This article flushed all my doubts. Thanks a lot again. God bless u.

  66. freggel says:

    Thanks for this article, but I have still one question.

    Does this mean that it also still uses the machine.config from the .net framework 2.0?

  67. Kashyap says:

    Thank God! I was not the only one to get confused with this.

    But your article made everything clear. Superb! Thanks a lot!

  68. Harish says:

    Very good article. Thank you very much.

  69. Sharon says:

    Thanks for the info – helped a lot to clarify this 3.5 install process, and it’s end results.

  70. Rock says:

    Thanks for this . it is very clear.

  71. Puneeth says:

    Thanks for the information, very useful!!!

  72. Rapolu says:

    Thanks a lot for the Info. Good Atricle

  73. bonisagus says:

    Great article. It explains very clearly.

  74. tyahid3 says:

    Excellent information.. I have been looking for this info for 2 days and finally got my website to work…

  75. KIra says:

    Thanks! Simple yet very informative.. πŸ™‚

  76. SV says:

    Superb Explanation !!!

    Thanks a lot !

  77. Sandy says:

    Very good explaination but I am having a problem here.

    I recently converted a 1.1 application to 3.5 and everything works fine on local machine. But when its moved to server, i am getting error saying "script manager is not known element". Please help. I have System.Web.Extensions included in my config.

  78. Sandy says:

    Finally I got it resolved. I enabled scripts on the permission tab. And then app worked fine.

    But I appreciate your article. Its solid.

  79. rainmanalex says:

    Couldn’t have said it any better and simpler Thanks a lot

  80. zorkmead says:

    This article was clearly written and very useful.  Thank You

  81. Gunasekaran says:

    Really a nice article keep up the things!!!!

  82. Mac says:

    I hate to be the guy who isn’t posting a "thank you" but I think your presentation is misleading. There is no such thing as ASP.NET 3.5. Microsoft marketing actually deserves most of the blame. ASP.NET has only proceeded to version 2.0. The .NET Framework is versioned separately and has had a 3.0 and 3.5 release.

    So it isn’t really correct to say that ".NET 3.5 isn’t a stand-alone framework" in this context because the .NET Framework version doesn’t bear any direct relationship to the ASP.NET version number.

    Just ran across this while looking for something else. πŸ™‚

  83. Ric says:

    This blog post saved me a lot of time. Thanks!

  84. Raj says:

    Thanks & Saved my time as well.

  85. Jonas says:

    Thanks! This article answered all my ASP.NET 3.5 confusions in one place. πŸ˜‰

  86. suvarna says:

    Recently we have migrated our code frm 1.1 to 3.5 and i was searching for 3.5 option under asp.net version but i cudn’t get it and i have been searching for this since a long time and finally i got this nice explanation here. Thanks for the useful information…this has answered all my questions.

  87. Julian says:

    hi, i from argentina, MUCHAS GRACIAS πŸ˜€ thank you!!

  88. Sanal Chandran says:

    Thanks a lot…. Very nice article…

  89. Harsha says:

    This is great. I was starting to sweat when I did not see the 3.5 version under IIS.


  90. Natalya says:

    I like many other was puzzeled, not anymore… Thank you so much for the explanation.

  91. roor says:

    thanks very much, it was very helpful article

  92. chad says:

    How can you tell 3.5 SP1 is installed 3.5.1 on the versions?

  93. MSP says:

    Really good and helpful. I was running like like a headless chicken to fix (!?!) this problem.

  94. Jasmine2501 says:

    Thanks very much for your help! But I have another problem…

    I installed ASP.Net and the .Net Framework 3.5, and now I’m trying to get a duck to eat cotton candy… can you please help me?

  95. Tanmoy says:

    After successful install of .net fw 3.5 on windows 2003 server, I went straight into ASP.NET tab and found 3.5 missing in the dropdown list! got no clue even after going through readme etc… and finally stumbled upon this article.

    Simple and to the point explanation. Bravo! Excellent.

  96. Sonali says:

    Thank you very much for this article. You have explined in very much details and in a very simple language.

  97. Ravikumar says:

    Good Article. It saved my time

  98. Niki says:

    Thank you very much…… This is  great…

  99. Nageshwar says:

    very good article about asp.net framework for iss

  100. Falgun D. Ruparelia says:

    Excellent Article, exactly the same information for which i was looking for.. Solved lots of confusion going in mind….

    Thanks ..

    Keep it up

  101. Gökçer Gökdal says:

    Thanks a lot! I knew situation and was not expecting 3.5 on IIS but I didn’t know why it was πŸ˜‰ Really simple, elegant and complete article. Thanks again!..

  102. Narayana says:

    Great article!  Thanks a lot for the details…  I wondered for a while why 3.5 option is not in the IIS manager

  103. sujan says:

    i have created one wrapper class to a smart card api, it works fine when i use source code and press f5, but not after creating virtual directory. i am using IIS 6.0 with on Win XP

    thanks in advance.

  104. Jimbo says:

    Thanks a lot.  This time from Spain. I spent over 2 hours trying to find the way to "attach" framework 3.5 to IIS just to find out it was allready done.

  105. Armando says:

    tengo mi aplicacion hecha en asp.net 3.5 sobre iis 5.1, el servidor iis 5.1 funciona, pero no corre mi aplicacion web; me sale un mensaje: error al compilar v 3.5.


  106. Richard says:

    Is Microsoft insane?!  Why do they make installs like this so difficult and why don’t they just say on the page where you download 3.5?  

  107. Harsh Gandhi says:

    Great…..Very usuful onformation

  108. keyur soni says:

    Grate artical …………………………………….

    very very very helpful.

  109. Shmul says:

    Thank You.

    found my answers here


  110. Mac says:

    thanks for content. Old project i use vs2005 and ajax control toolkit 2.0 after i install vs2008 and change ajax2.0 to ajax3.0 and i deploy project to framwork3.5. can i crate deploy web site in iis and run it?

  111. Thanks! says:

    Simple and easy language, too the point, solved problem for me.

  112. Tony Jose says:

    Hi everyone here…

    You wont find ASP.NET 3.5 on IIS probably because ASP.NET 3.5 uses the same ASP.NET 2.0 engine.

  113. Parissa Bakhshi says:

    Thank you, now I can stop searching about registrering .Net 3.5 in IIS! Can do ths with 2.

  114. Brian T says:

    Thanks for this, was looking for they .net 3.5 is IIS tab

  115. NC2 says:

    Thank you for enlighting on v3.5 and "ASP.Net Version" in IIS. It cleared my adoubt deploying my vs2008 app with v2.x as "ASP.Net Version".

  116. Akbar MD says:

    Hi Vijay,

    Very good explanation with good use of pictures. You have cleared all my doubts.

  117. A says:

    Great Article. Very helpful to understand where I was confused. Thank you very much for sharing this !

  118. Abithakumar says:

    Very very good article…

    Thanks for your suppor

  119. PJ says:

    Still useful, and relevant, three years on, thanks πŸ™‚

  120. Ashish Salvi says:

    Thank you so much. You explanation clear out my doubt.

  121. Aash says:

    Great Article!! thanks!!!! simple, clear, consice and accurate!! i was confused for months about this issue… thanks once again …. keep up the great work πŸ™‚

  122. Ben says:

    Excellent Article.I was wondering why 3.5 was not listed under ASP.NET tab in IIS.

  123. Scott Daniel Lentz says:

    Thank you for letting us all know what Microsoft assumes you know, as if you worked on the .Net project.

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