22

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:

enter image description here

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!

Tseng
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James Ko
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  • 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. https://github.com/dotnet/corefx/blob/master/Documentation/architecture/net-platform-standard.md You'll need at least multitargeting `net451` and `net40` to support both, 4.0 and (ASP).NET Core against Full .NET Framework/Mono – Tseng Mar 20 '16 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 Mar 20 '16 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 Mar 21 '16 at 01:45
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    @LexLi Yes, but for simple libraries ([like this](https://github.com/jamesqo/Enumerator/blob/master/src/Enumerator/project.json)) that don't require async support, targeting .NET 4 isn't too much of an issue. – James Ko Mar 21 '16 at 02:13
  • Thanks for this question! I couldn't find anything until now. Really helped a lot. – Jossean Yamil Jun 23 '22 at 16:01

3 Answers3

33

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.

Simon_Weaver
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mstaessen
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  • 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.' – James Ko Mar 20 '16 at 20:41
  • 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) – joe Jul 24 '19 at 06:35
17

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).

multi-target switcher visible

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):

multi-target switcher not visible

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

enter image description here

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 indenpendently for any file open in editor.

superjos
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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.

enter image description here

There's also another pick below your tab bar:

enter image description here

Luke Vo
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