Should I use .NET 4.0 or 4.0 Classic on a Windows 2003 Server? RRS feed

  • Question

  • I've got an older WCF service which I wrote 5 years ago, using VS 2008. I am working on upgrading it, adding new functionality, etc. It's my understanding that Windows Server 2003 R2 doesn't support the .NET Framework 4.5, so I'm doing my development with VS 2010 and using .NET 4.0. I do, however, have VS 2012 and .NET 4.5 installed on my development machine. Furthermore, this WCF service runs user IIS. When I configured the WCF to run under 4.0 in IIS, I saw that there were 2 application pools it could run under. One was called .NET Framework 4.0, and the other was called .NET Framework 4.0 Classic. Since I was doing this on my development machine (now a Windows 7 Ultimate 64-bit box) with VS 2010 and VS 2012 both installed, I was wondering if the .NET Framework 4.0 Classic referred to the .NET Framework 4.0, whereas teh .NET Framework 4.0 was really 4.5?

    Which should I use for development in IIS on my dev box and which should I use on the Windows Server 2003 R2?


    Wednesday, March 6, 2013 2:41 PM


  • Hi,

    If you mean Integrated or Classic Managed Pipeline mode, Classic mode (the only mode in IIS6 and below)  is a mode where IIS only works with ISAPI extensions and ISAPI filters directly;Integrated mode, on the other hand, is a new mode in IIS7 where IIS  pipeline is tightly integrated (i.e. is just the same) as ASP.NET  request pipeline. You can refer a post here.

    As you said, .NET 4.5 is not work on windows server 2003 R2, but you can run .NET 4.0 in windows server 2003 with iis 6, but there may be some problems, please refer:


    Best Regards. 

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    • Proposed as answer by cheong00 Thursday, March 7, 2013 7:32 AM
    • Marked as answer by Rod at Work Thursday, March 7, 2013 3:06 PM
    Thursday, March 7, 2013 7:03 AM