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Will Visual Studio upgrade project files accordingly?

Falanga, Rod, DOH 80 Reputation points
2024-04-29T20:26:12.4766667+00:00

I may have an old .NET Framework app dumped into my lap. I've been looking at it for a while, to try and wrap my head around it. It's got 18 projects in the solution file, comprised of 5 different .NET Frameworks. Everything from .NET Framework 2, to 4.5.1. I've heard it said that when Microsoft upgraded from one of the old .NET Frameworks to another .NET Framework, that sometimes the project file would change radically. I'm thinking of upgrading all of them to .NET Framework 4.8. (I probably couldn't get buy in from management to go to .NET 6 or 8, which I'd rather do. They're extremely resistant to anything like that.)

So, my question is, if I use either VS 2022 or 2019, would they properly upgrade the project file as I go from .NET Framework 2 to 4.8, etc.?

Visual Studio
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A family of Microsoft suites of integrated development tools for building applications for Windows, the web and mobile devices.
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.NET Runtime
.NET: Microsoft Technologies based on the .NET software framework.Runtime: An environment required to run apps that aren't compiled to machine language.
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  1. Michael Taylor 48,976 Reputation points
    2024-04-29T20:37:16.6366667+00:00

    You can use VS 2022 to open older NET Framework projects. In general there are no changes that it'll actually make unless the solution was created in a really, really old version of Visual Studio. Irrelevant it will just load them up.

    Now, if you attempt to load a project that requires a framework that is not currently installed (older or newer) then VS will pop up a message with several options. The most likely option is to auto-install the missing framework. If you don't want to upgrade anything then this is the way to go. However anything before NET 4 isn't supported at all so that won't be an option anyway. The other option is to go ahead and update the projects to the newer NET Framework version (4.8). If you intend to upgrade the projects then you might as well go this route anyway. It'll just update the project files.

    Now the fun starts. In general if you previously targeted NET 4.x then updating to the newer framework is pain free and won't require any changes beyond the target framework update (which is automatic or can be done via the project properties UI) and updating any NuGet dependencies to the newest version (which you should do anyway). Of course any code that was deprecated or removed will no longer work and there may be language changes that cause some code to fail compilation but these are generally pretty easy to fix up. Once you're done though the upgrades are complete.

    For the pre-NET 4 projects though you may have more work to do. Ideally it'll just auto-upgrade and you follow the previous steps. However if you have config files and they had settings that are no longer supported then you need to clean them up. Most likely there are also project settings that aren't needed anymore but shouldn't hurt anything. Honestly it might be easier to just create a new NET 4.x project and copy all the code over and then remove the old project. This will at least clean out any legacy settings.

    What people are referring to when they say the project file has changed is when you migrate from NET Framework 4.x to NET Core/5/6/7/8. The newer frameworks use an SDK-format which is quite a bit different and simpler. Once you are ready to upgrade to the newest NET Core runtime then you'll have to convert. Fortunately MS has an Upgrade Assistant extension you can install that can make the project (and some related) changes for you. Alternatively there are a couple of custom extensions floating around that do it as well. Ultimately it is a big change so I wouldn't bother until you are on NET Framework 4.x.

  2. Bruce (SqlWork.com) 57,481 Reputation points
    2024-04-29T22:40:08.2566667+00:00

    the migration worked best back when it was current (1.1 => 2.0 => 3.5 => 4.0). the project file also has the visual studio version which defines the toolset used to build.

    this is how you current project works:

    https://learn.microsoft.com/en-us/dotnet/framework/migration-guide/how-to-configure-an-app-to-support-net-framework-4-or-4-5

    you can try the migration tools (unfortunately most of the pre 4.6 migration information is lost):

    https://learn.microsoft.com/en-us/dotnet/framework/migration-guide/migrating-from-the-net-framework-1-1

    and sometimes they work. sometimes not. often creating a new project, and adding the source is an easier option.

    migrate the top level projects first.

    note: you will want to use version control, and save state as you progress.

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