I'm attempting to build a .net application on linux and when I do dotnet restore it is ignoring my TargetFramework from my .csproj and attempting to build an older version of .net

Phillip Davis 1

As noted in the title. I set the TargetVersion in the .csproj to net60 and when I do a dotnet restore to get the nuget packages it gets them and then fails saying that the nuget libraries I'm attempting to use are for net451 or greater and I'm attempting to build net40 I don't see how/where I am getting overridden. (BTW this is an older .net35 app I'm attempting to migrate to newer .net and on linux etc. Not even sure if anyone's done that before.

Here's the detailed output of the things I see that's showing it 'worked' to select net60:

Target "_GetRestoreTargetFrameworksOutput" in file "/usr/share/dotnet/sdk/6.0.200/NuGet.targets" from project "/home/pdavis/src/myapp/src/myapp/myapp.csproj" (target "_GenerateResto
reProjectSpec" depends on it):
Using "GetProjectTargetFrameworksTask" task from assembly "/usr/share/dotnet/sdk/6.0.200/NuGet.Build.Tasks.dll".
Task "GetProjectTargetFrameworksTask"
(in) ProjectPath '/home/pdavis/src/myapp/src/myapp/myapp.csproj'
(in) TargetFrameworkMoniker '.NETFramework,Version=v4.0'
(in) TargetPlatformIdentifier 'Windows'
(in) TargetPlatformVersion '7.0'
(in) TargetPlatformMinVersion '7.0'
(in) TargetFrameworks ''
(in) TargetFramework 'net60'
(out) ProjectTargetFrameworks 'net60'

I got a bit confused if I should use 'net60' or 'net6.0' but tried both and get the same behavior.

Why is it setting the TargetFrameworkMoniker incorrectly when I set the targetframework to net60?

Phillip Davis 1 Reputation point

2022-03-09T21:12:16.117+00:00

Oh I should add, here's the error output on the dotnet restore:

error NU1202: Package System 4.1.311.2 is not compatible with net40 (.NETFramework,Version=v4.0). Package System 4.1.311.2 supports: net451 (.NETFramework,Version=v4.5.1) [/home/pdavis/src/myapp/myapp.sln]
/home/pdavis/src/myapp/src/myapp/myapp.csproj : error NU1202: Package System.Net.Http 4.0.0 is not compatible with net40 (.NETFramework,Version=v4.0). Package System.Net.Http 4.0.0 supports: [/home/pdavis/srcmyapp/myapp.sln]

(Note all my paths for all my code live in /home/pdavis/src/ so the root of the project is /home/pdavis/src/myapp

~Phil
P a u l 10,406 Reputation points

2022-03-09T21:12:23.073+00:00

Just to clarify, your project is currently targeting .NET Framework 3.5 and your aim is to upgrade it to .NET 6.0?
Phillip Davis 1 Reputation point

2022-03-09T21:16:45.417+00:00

Correct, I'm first trying to update all the included libraries to the latest versions and then will proceed to fix them to build and/or refactor code to use newer replacement methods or libraries if old ones are deprecated etc. But I'm first trying to get past this stage to start looking over the problems with the includes. It's a really old app they keep wanting to EOL but it just ain't happening so to improve it's security posture I'm trying to update it to newer/safer/more supported .net and libraries.

Pie in the sky dream is on linux in .net60 if not, then I'll move over to windows and whatever is a currently supported .net and latest windows server.

~Phil
P a u l 10,406 Reputation points

2022-03-09T21:38:45.59+00:00

I think there are a few issues you'll run into porting projects that old - .NET Framework 3.5 and .NET 6.0 were released 15 years apart. .NET Framework was/is also heavily dependent on Windows and relies a lot of native Windows components, so finding replacements might not be a 1-for-1.

Here's a helpful website that details all versions of .NET Framework + .NET (previously called .NET Core, but rebranded to .NET after version 5.0):
https://versionsof.net

If your aim is to just to improve the project from a security point of view you could consider aiming to upgrade it to .NET Framework 4.8 instead. Currently .NET Framework 4.6.2 - 4.8 are still receiving security updates & there's no plan to drop support for them because of how many apps still rely on .NET Framework:
https://learn.microsoft.com/en-us/lifecycle/products/microsoft-net-framework

That would mean sticking with Windows for the time being, but not having to deal with ditching all your native dependencies for the sake of security. It's also more likely that your existing Nuget packages will still compatible with your existing project. If your aim is to switch to .NET 6.0 regardless then it's definitely worth having a run through a migration guide so you can resolve as many common issues as possible:
https://learn.microsoft.com/en-us/dotnet/core/porting/

Have you switched over to the new csproj file format?
Phillip Davis 1 Reputation point

2022-03-09T21:58:26.293+00:00

I'm using a .csproj file, it already existed in the old .net35 app,

I'm not sure if you're meaning there's been a schema update/format update?

Either way, that is definitely one of my thoughts/options was to go to a supported version like 4.8

How can I go to 4.8 if I tell it to build that and it keeps trying 4.0? That's the biggest problem/mystery I'm seeing here.

Thanks for the information and help.

~Phil
P a u l 10,406 Reputation points

2022-03-09T23:04:42.393+00:00
Correct - the csproj format changed a lot between .NET Framework & .NET Core to trim out a lot of noise - for some projects it may be easier to just create a new project and copy things over, but here's a basic conversion guide:
https://natemcmaster.com/blog/2017/03/09/vs2015-to-vs2017-upgrade/

If you're still on the old style of csproj then I don't believe it's possible to target .NET Core (1.0 - 3.1) or .NET 5/6 as they're incompatible.

The target framework is specified differently between .NET Framework / .NET Core so you just need to make sure you're not mismatching them:
https://learn.microsoft.com/en-us/visualstudio/ide/visual-studio-multi-targeting-overview?view=vs-2022#change-the-target-framework

From the above article:

Depending on the target framework, it can be represented in the following ways in the project file: For a .NET Core app: <TargetFramework>netcoreapp2.1</TargetFramework> For a .NET Standard app: <TargetFramework>netstandard2.0</TargetFramework> For a .NET Framework app: <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>

So because yours is a .NET Framework app if you wanted to upgrade to .NET Framework 4.8 you could just set:

<TargetFrameworkVersion>v4.8</TargetFrameworkVersion>

In your csproj (provided that framework version is installed on your dev machine)
Phillip Davis 1 Reputation point

2022-03-10T01:39:52.16+00:00

Ok, I loaded the project in visual studio 2022 and it asked me to update to 4.8. I did so and it seems to have compiled just fine, and I've also updated all the libraries as well to the latest and greatest and it's building. I'll research doing the other move you mentioned.

Thanks!

~Phil