No .NET 4.5 for XP/2003

Microsoft has just declined a UserVoice request that the upcoming .NET 4.5 should be made available for Windows XP and Server 2003. With 3,322 votes this was the second most popular request on Microsoft’s own feedback site, proving once again that actively providing any sort of feedback to Microsoft is generally a waste of time.

Why this request? The problem is that .NET 4.5 is an in-place upgrade for 4.0 that fixes a number of significant bugs in the older version. Once you install .NET 4.5 on your developer machine, you can still target .NET 4.0 – but what you’re actually running is an updated 4.0 subset of 4.5 rather than the .NET 4 that’s installed on your XP/2003 deployment machines. As discussed on the MSDN Forums, this means that you cannot test for errors that are specific to the older version. You’ll need to reserve an actual 4.0 machine for that. Even worse, both Visual Studio 2012 and Windows 8 will ship with .NET 4.5 – so if you need to target .NET 4 on XP/2003 you cannot use either product!

This is a very big deal for enterprise developers who must support .NET applications on XP/2003 machines for years to come. Microsoft’s own support for these operating systems extends to 2014/15, making this decision even more incomprehensible. Faced with the choice of either upgrading all their Windows XP/2003 installations or not upgrading to Visual Studio 2012 and/or Windows 8, what do you think most companies will do?

2013-05-14: The decision to make .NET 4.5 an in-place upgrade to 4.0 causes conflicts with Microsoft’s own tool chain. As Steve Johnson noted on Stack Overflow, the underlying debug APIs changed significantly between 4.0 and 4.5, such that you cannot debug a .NET 4.0 dump with the .NET 4.5 SOS.dll. You’ll need to manually copy over SOS.dll from an actual .NET 4.0 machine! Michael Stum describes the error and remedy in greater detail.

2016-05-03: Microsoft has put up a comprehensive Introduction to .NET Framework Compatibility which explains the situation and gives advice on how to handle compatibility issues. At the time of this writing, new .NET 4.x releases continue to be installed as in-place updates.

11 thoughts on “No .NET 4.5 for XP/2003”

  1. Yes. Microsoft definitely did not have our backs on this one. Sometimes I wonder MS Marketing think that the entire world consists of just games, office extensions, CRUD clients and web apps.

  2. Agree, except for one sentence: “Even worse, both Visual Studio 2012 and Windows 8 will ship with .NET 4.5 – so if you need to target .NET 4 on XP/2003 you cannot use either product!”

    This is not correct, with VS2012 you can still target your application to .NET 4, and applications targeted .NET 4 will also run on Windows 8.

    1. Jackie, please read two sentences earlier: “You can still target .NET 4.0 – but what you’re actually running is an updated 4.0 subset of 4.5 rather than the .NET 4 that’s installed on your XP/2003 deployment machines.” That’s what I meant.

      I was informed that Microsoft does attempt to emulate some 4.0 bugs when you’re targeting 4.0 on a 4.5 system, but you have to trust them to correctly emulate the bugs you need.

  3. Windows XP is near to death, it’s an old generation OS and Microsoft is pushing more and more people to update to newer systems. I am not surprised that .NET 4.5 doesn’t run on XP, event if this is technically possible. Same for Internet Explorer 9 (why all other browsers run on XP). It’s business strategy.

    I’m in the process of analyzing other alternatives to .NET just for this reason. And the best candidate for my projects is Mono.

    1. Developers may have no choice but to use Windows XP as most companies refuse to upgrade the OS. As for me, I’m stuck with IIS 6 (Widows Server 2003), because there is no funding to upgrade. So I am using .net 4.0 at the risk of bugs, and 4.5 simply isn’t an option for me, unless I decide to be generous and donate the cost of Windows Server 2012 to the company I work for!

      Our company is just now upgrading to Windows 7. Most computers here are still using Windows XP and will not be upgraded until new hardware is needed due to component failure. It might be another couple of years before we are completely upgraded to Windows 7, let alone Windows 8!

      This is not an unusual situation for many companies. I’ve worked in other, even bigger companies and they do the same thing. This is the way things are in the real world…

  4. I would like to see the .NET framework dropped COMPLETELY. As a power user of Windows XP, Vista, 7 and 8, I can tell you with great emphasis that the .NET framework has been the bane of my existence for many years. When it breaks, it breaks BADLY requiring a “.NET Framework Cleanup Tool” that might help you restore functionality. However, in more cases you are stuck with little or no help from Microsoft as their tech docs are quite useless in repairing problems to the .NET framework. So, let me suggest another course of action: STOP USING .NET COMPLETELY. If you’re writing software, write it properly and don’t depend on a big, bulky, bug-filled common library set to do your work. Write software so that it doesn’t require this horrible dependency. PLEASE. OMG.

  5. This is called programmed or planned obsolescence ( Not because the software is going to fail, but because its technology provider decides not to support it any more.

    It is the artificial mechanism they have to push you to acquire new technologies and new versions of current products, keeping you paying for stuff that will sustain their value and wealth.

  6. Much as I dislike being forced to do anything… we cannot expect Microsoft to continue to support ancient operating systems. Metro UI aside, Windows 8/ server 2012 continue to house major technology improvements. Those improvements require a lot of money and development resources to create. It is not realistic to expect MS to devote skilled resources to maintaining old versions of their software forever, any more than you would allow a small subset of your own customers to force you into leaving your software products in a rut. Customers want improvements! If your products don’t provide them, they seek alternatives.

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