CODEWITHSUNDEEP
.net
daisy
daisy

Reputation: 23489

Why is program compiled with .NET 3.5, can't run with .NET 4?

I have a program compiled with .NET 3.5 and when I copy it to a Windows Server 2016 box, that only have .NET 4.X installed, it just won't run.

And it prompt me to install the .NET 3.5 framework.

enter image description here

Isn't .NET backward compatible? Is there a way to run that program with .NET 4 directly?

Upvotes: 0

Views: 1548

Answers (1)

Wai Ha Lee
Wai Ha Lee

Reputation: 8805

.NET 4.x versions are in-place upgrades for earlier .NET 4.x versions (e.g. 4.6.2 is an in-place upgrade for 4.6.1, 4.6, 4.5.2, 4.5.1, etc.). That way, you can have applications which target (for example) .NET 4.6.2 and .NET 4.5.2 running side-by-side - the framework takes care of it. That is, however, for .NET 4.x versions.

For earlier versions, see Version Compatibility in the .NET Framework on MSDN, especially the section "Compatibility and side-by-side execution" which says (emphasis mine):

If you cannot find a suitable workaround for your issue, remember that the .NET Framework 4.5 (or one of its point releases) runs side by side with versions 1.1, 2.0, and 3.5, and is an in-place update that replaces version 4. For apps that target versions 1.1, 2.0, and 3.5, you can install the appropriate version of the .NET Framework on the target machine to run the app in its best environment. For more information about side-by-side execution, see Side-by-Side Execution.

You mention that you "have a program compiled with .NET 3.5" - if that means you have access to the source code, you could try to change it to target a more recent version of the .NET framework (for instance, the 1809 build of Windows 10 comes with support for .NET 4.7.2 built-in; Windows Server 2016 has .NET 4.6.2 built-in). If that isn't possible (there will be some breaking changes that you'll have to deal with) then it looks like you will have to install the .NET framework 3.5 on each machine that you wish to run the application on.

Failing that, you can try to edit/add the app.config file to force the application to run using .NET 4.6 - see How to: Configure an App to Support .NET Framework 4 or 4.5 for details, but the jist is:

To configure your app to run on the .NET Framework 4 or 4.5

1) Add or locate the configuration file for the .NET Framework project. The configuration file for an app is in the same directory and has the same name as the app, but has a .config extension. For example, for an app named MyExecutable.exe, the application configuration file is named MyExecutable.exe.config.

To add a configuration file, on the Visual Studio menu bar, choose Project, Add New Item. Choose General from the left pane, and then choose Configuration File. Name the configuration file appName.exe.config. These menu choices are not available for Windows Store app or Windows phone app projects, because you cannot change the activation policy on those platforms.

2) Add the <supportedRuntime> element as follows to the application configuration file:

<configuration>  
  <startup>  
    <supportedRuntime version="<version>"/>  
  </startup>  
</configuration>

where specifies the CLR version that aligns with the .NET Framework version that your app supports. Use the following strings:

  • .NET Framework 1.0: "v1.0.3705"
  • .NET Framework 1.1: "v1.1.4322"
  • .NET Framework 2.0, 3.0, and 3.5: "v2.0.50727"
  • .NET Framework 4 and 4.5 (including point releases such as 4.5.1): "v4.0"

Upvotes: 4

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