How to switch between target frameworks for .NET Core projects in Visual Studio

Question

Say you have a .NET Core project that looks like this:

"frameworks": {
    "net40": {},
    "dotnet5.1": {}
}

And this is your C# code:

public class Foo
{
    public static void Blah()
    {
#if DOTNET5_1
        DoSomething();
#elif NET40
        DoSomethingElse();
#endif
    }
}

Now, in Visual Studio when you view the .cs file, one of the #if sections will be grayed out- either DoSomething or DoSomethingElse. Here's how it shows up on my laptop:

Is it possible to get VS to 'switch context' between target platforms, so you can view what would be compiled for a particular platform? For example, I might want to check for any red squiggly lines for each framework before actually building the solution.

Any help would be appreciated, thanks!

On a side note, why are you targeting net40? Your class library won't be compatible with .NET Core running against the full .NET Framework as the minimum supported Version is .NET 4.5.1. github.com/dotnet/corefx/blob/master/Documentation/architecture/… You'll need at least multitargeting net451 and net40 to support both, 4.0 and (ASP).NET Core against Full .NET Framework/Mono — Tseng
– Tseng, Commented Mar 20, 2016 at 20:25
@Tseng Refer back to the document you linked. dotnet5.1 will take care of .NET 4.5, Windows 8, and most other platforms. net40 will take care of .NET 4.0. — James Ko
– James Ko, Commented Mar 20, 2016 at 20:31
@JamesKo Since most sync methods are removed in favor of async alternatives (in sockets and so on), targeting .NET 4 would be tricky. Also .NET 4 is end of life and .NET 4.5.2 is the new base line. — Lex Li
– Lex Li, Commented Mar 21, 2016 at 1:45
@LexLi Yes, but for simple libraries (like this) that don't require async support, targeting .NET 4 isn't too much of an issue. — James Ko
– James Ko, Commented Mar 21, 2016 at 2:13
Thanks for this question! I couldn't find anything until now. Really helped a lot. — Jossean Yamil
– Jossean Yamil, Commented Jun 23, 2022 at 16:01

Simon_Weaver · Accepted Answer · 2016-10-27 14:23:53Z

42

At the top of your editor should be the navigation bar. Left in the navigation bar is a dropdown menu that lets you select the context.

If the navigation bar is hidden, you can enable it by going into Tools > Options > Text Editor > C# and check the navigation bar checkbox.

edited Oct 27, 2016 at 14:23

Simon_Weaver

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answered Mar 20, 2016 at 20:09

mstaessen

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2 Comments

James Ko Over a year ago

Thank you so much! I think that was my main problem, I didn't know there was a navigation bar available so I was confused when VS said I could use the 'nav bar to switch context.'

joe Over a year ago

Note that this only change the view and intellisense. To chose which target to run against, check the dropdown list of the "start to debug" button. (VS2017/2019)

superjos · Accepted Answer · 2024-08-08 14:24:01Z

Answer already provided seems mostly correct. I'd just like to highlight some issues currently present with that.

As of today, on VS 2015 Community Ed, Version 14.0.25424.00 Update 3, global.json sdk 1.0.0-preview2-003121, the nav bar shows multiple targets only if the startup project is a multi-target "executable" one (e.g console app).

If startup is set on a multi-target class library, no target switch is listed (and the label next to the green arrow is different as well):

Also, when switcher can be used, it seems like "standard" conditional defines provided by build system are not correctly highlighted in editor:

In order to see conditional define blocks correctly highlighted, one has to switch the project switcher, highlighted in green in last screenshot. It seems like different targets in same project are treated as different projects to this purpose. And that can be changed independently for any file open in editor.

Luke Vo · Accepted Answer · 2022-11-25 05:10:47Z

0

I came to this question because I am working on MAUI project. To choose between targets, click on the triangle icon on the right of the Debug button, then Framework, then select the environment you want to work with.

There's also another pick below your tab bar:

edited Nov 25, 2022 at 5:10

answered Nov 25, 2022 at 4:38

Luke Vo

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