I have a project running .NET Framework 4.8 and in the project's properties under "Build > Advanced > Language Version" Visual Studio states "Automatically selected based on framework version". Wouldn't it be great, if they were to show me which version was automatically selected? :o/
According to https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/configure-language-version (amongst others) my project should be using C# 7.3, but I cannot use the latest features. "Latest" as in "as far as Microsoft will let me go with the old .net Framework".
How can I determine which C# version is being used and how can I update to the "latest" version?
I have no idea if it is possible to view the currently selected lang version from within visual studio. But it is fairly easy to specify the latest version.
From the same article you linked, edit your csproj file in a text editor and add the line <LangVersion>latest</LangVersion>, For example:
<PropertyGroup>
<LangVersion>latest</LangVersion>
</PropertyGroup>
You should also be able to specify preview as the langversion to get the preview version.
Note that not all language versions are supported for all .net platforms, so using this on .Net framework might not technically be supported. But I have been running the latest version on .net 4.8 and not noticed any major issues so far. The most noticeable issue is having to manually edit all the csproj files.
I recently start to work on a legacy ASP.NET codebase based on .NET framework 4.0. We managed to pass everything from Visual Studio 2012 to VS 2017, updated the build server with a new version of Jenkins and installing .NET framework 4.7.x.
Locally we can write C# code of the newest version (7.3) and the build works (VS doesn't use MSBuild if I remember right), but when we deploy on the build server the build fails because there MSBuild cannot recognize constructs newer than C# 4.0. To avoid mistakes I fixed the lang version to 4.0 (advanced build properties on projects), so if I write too new C# VS blocks me in dev, but we would like to start using new C#.
We also tried to fix C# 7.3 directly in the project (<LangVersion>7.3</LangVersion> in PropertyGroup inside csproj) and the but ToolsVersion property of Project element (csproj) to 14.0, but then building we MSBuild fails with the error:
CS1617: Invalid option ‘6’ for /langversion; must be ISO-1, ISO-2, 3,
4, 5 or Default
Here it's explained that what I want to do it is possible: https://www.dotnetcurry.com/dotnet/1427/build-apps-different-dotnet-framework-versions
No matter which .NET framework version we target in the project, the
C# language version in use will not change. That’s fine because the
vast majority of language features that were introduced in later
versions of the language don’t depend on the CLR or specific APIs.
They are only syntactic sugar and the bytecode generated by the
compiler will still work in .NET framework 2.0.
Anyone have an idea of what mistake are we doing?
The problem was that on the build server MSBuild wasn't properly installed and build scripts got an old one.
Installing Visual Studio 2017 Build tools and fixing the path on the script we solved.
After we had the problem "The “GetReferenceNearestTargetFrameworkTask” task was not found" we solved like explained here: The "GetReferenceNearestTargetFrameworkTask" task was not found
(the right answer depends on what strategy have you used to install VS Buld tools).
There was time I thought that the Framework version and the C# version are the same things, so once you install the next Framework version on the computer, you should use it.
Then I found out that the framework is not linked directly with the C# version, and on the same machine multiple C# compilers can be cohabitate, so probably the compiler and C# version should be the same.
Now I understand that the compiler version and the C# version are not the same...
Visual Studio Command Prompt (2010): C:\>csc
Microsoft (R) Visual C# Compiler version 4.0.30319.33440
for Microsoft (R) .NET Framework 4.5
Developer Command Prompt for VS 2013: C:\>csc
Microsoft (R) Visual C# Compiler version 12.0.30110.0
for C# 5
we can see that
- VS 2010 uses a compiler version 4.0 for the C#4 (?? I just can suppose it, because not explicitly mentioned);
- VS 2013 uses the compiler version 12.0 fo the C# 5 (this is explicitly mentioned)
Knowing that compiling using different language versions could bring different results to the user
Questions
How to find out what C# version (not the compiler one, but the language one) uses VS to build my concrete project?
Is there a strict, clear and transparent link between the C# compiler and language versions?
Can I indicate to Visual Studio (in case of migration issues from one Studio version to another) to use different compiler version for my concrete solution?
As nobody gives a good enough answer, I will have a try now.
First, C# has its version history published by Microsoft now (coming from MVP posts obviously),
https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-version-history
So you can easily see what new features are added for each new releases.
Second, we will talk about the compiler releases, which initially were part of .NET Framework.
Below I list a few milestones (might not be 100% correct, and some versions might be skipped),
csc.exe 1.0 (?) for .NET Framework 1.0 (implements C# 1.0).
csc.exe 2.0 (Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.8745) for .NET Framework 2.0 (implements C# 2.0, as well as 1.0 for compatibility).
csc.exe 3.5 (Microsoft (R) Visual C# 2008 Compiler version 3.5.30729.8763) for .NET Framework 3.5 (implements C# 3.0, and older versions).
csc.exe 4.0 (?) for .NET Framework 4.0 (implements C# 4.0, and older).
csc.exe 4.x (like Microsoft (R) Visual C# Compiler version 4.7.2053.0) for .NET Framework 4.5 and above (implements C# 5.0, and older). Note that the version numbers vary a lot (from 4.x to 12.x) based on the .NET Framework on your machine (4.5.0 to 4.7.1).
Then Microsoft made the old csc.exe obsolete (as they were native executable), and shipped Roslyn based compiler instead (though still csc.exe). In the meantime, C# compiler is no longer part of .NET Framework, but part of VS.
It was the same time, that C# compiler, language version, and .NET Framework are fully decoupled, so that you can easily use multi-targeting.
Roslyn csc.exe 1.x (?) implements C# 6.0 and older. Shipped with VS2015.
Roslyn csc.exe 2.x (like Microsoft (R) Visual C# Compiler version 2.4.0.62122 (ab56a4a6)) implements C# 7.x and older. Shipped with VS2017.
Ok, enough background. Back to your questions.
Q1: How to find out what C# version (not the compiler one, but the language one) uses VS to build my concrete project?
Answer: You can easily see from project settings that what language version is used.
If you don't choose an explicit version, it can automatically use the latest version supported by the csc.exe compiling the project.
Note that #Servy commented under #DaniloCataldo's answer about the langversion switch with more details. That switch has its design goals and limitation. So for example even if you force Roslyn 2.x compiler to compile your project based on C# 4.0, the compiled result would be different from what C# 4.0 compiler does.
Q2: Is there a strict, clear and transparent link between the C# compiler and language versions?
Answer: Please refer to the background I described above, I think that already answered this part. There is a strict, clear and transparent link.
Q3: Can I indicate to Visual Studio (in case of migration issues from one Studio version to another) to use different compiler version for my concrete solution?
Answer: A Visual Studio release (like VS2019) sticks to an MSBuild release (16.x), so a dedicate version of C# compiler. So in general Q3 is duplicate to Q1, as you can only change language version.
There are a bunch of NuGet packages to override C# compiler used by a project, such as https://www.nuget.org/packages/Microsoft.Net.Compilers.Toolset. However, Microsoft states that "Using it as a long term solution for providing newer compilers on older MSBuild installations is explicitly not supported", so you really shouldn't explore that route.
In the past Visual Studio 2005 was fixed only to one .Net version and C# compiler delivered with this version. In case you want use newer version of VS you have to switch Visual Studio as well. Now Visual studio can target to more than one .Net version and it can even mix new C# compiler with old .Net framework (lambdas or extension methods in .Net 2.0). Simply C# compiler version is related to C# language version.
You can check your compiler version in project file (open it as xml) and there is ToolsVersion attribute of Project element.
In my specific project there is ToolsVersion="4.0" and my target project is .Net 2.0. It means I can use new language construct in old framework which is not possible in VS2005.
Just to add to the previous answer.
You should be aware that while the C# language and the C# compiler are separate from .Net framework, they still depend on it.
For example, the C# 5 has await/async language feature, but you can't use it with the .Net 4, at least not without some extra actions and nuget packages.
On the other hand, you still can use the nameof or null propagation features of C# 6 with the .Net 4.0 because they are implemented purely by compiler
One way to tell the language version the compiler support is
csc -langversion:?
and get response like
Supported language versions:
default
1
2
3
4
5
6
7.0
7.1
7.2
7.3
8.0
9.0 (default)
latestmajor
preview
latest
To indicate to Visual Studio which language version to use there's a compiler option called /langversion
You can find more about it here.
It can be set programmatically too, as stated here.
The compiler can compile in different versions of the language, the language version is not directly related to that of the framework, but often to use a language feature there's a minimum framework for which it can work.
Just few minutes ago I have compiled in VS 2015 a dll which uses the string interpolation of c# 6.0
var version = 4;
var output = $"{version}";
and has the framework 4.0 as target.
It compiles and works fine.
This post explains versions entanglement, but only for older c# versions.
I want to install two different version of my WinForms custom control in the Visual Studio Toolbox: the .NET Framework 2.0 version and the .NET Framework 4.0 one. I found this professional solution http://vstudiotoolbox.codeplex.com/ but selecting the proper .NET Framework is not covered.
Where can I learn more?
Thanks.
http://www.lextm.com/2012/08/how-to-install-custom-controls-to-visual-studio-part-i/
This covers what is required to install a .NET 2 control. If you want to install .NET 4's, you can follow
http://www.lextm.com/2012/08/how-to-install-custom-controls-to-visual-studio-part-ii/
My open source project is a sample for you to review how to perform the needed steps,
https://github.com/lextm/actionlistwinforms
Inno Setup is used to author the installer, but the tricks should apply to other installer techniques.
I am porting a project built on VS2008 to VS2005 since the minor .NET version for us have to 2.0 instead of 3.5 and rest of our code is building on VS2005. So I modified the visual studio version from 2008 to 2005 at the .sln file
Microsoft Visual Studio Solution File, Format Version 9.00
# Visual Studio 2005
So I am able to load the .sln into the VS2005. I have some building problem, mainly the "var" and after I modified those lines with real data type, the code compiles and runs.
However at the project assembly reference. I found out that my code is still reference Linq which is from .NET 3.5:
C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.5\System.Xml.Linq.dll
When I open up the dialog to add new reference, I could see that the .NET version 2.0, 3.5 and even 4.0 (although the CLR runtime version is 2.0.50727 in most of cases. sometimes 1.x and sometimes 4.0, Linq's runtime version is 2.0.50727).
I thought that VS2005 only supports .NET 2.0 which seems not that case here. So I guess how can I make sure that my application would only require .NET 2.0 framework. Is it enough to make sure that I only reference .NET 2.0 and below reference?
As long as the target framework is .NET 2.0 and you don't reference any libraries that do target higher .NET framework versions, your app should run just fine on .NET 2.0.
That said, I believe Visual Studio 2008 supports multi-targeting, so you should be able to use VS2008 but still target .NET 2.0 as your output type. Additionally, VS2010 and VS2012RC also support .NET 2.0 only projects.
To answer the exact question in the title (for the benifit of those who find this page by its title) the .NET version used by default in Visual Studio 2005 is .NET v2.0.
You can still use VS2008. VS2008 fully supports 2.0-only projects (just change the project settings). When in 2.0 mode VS will disable any 3.0 and 3.5 assemblies as well as any C# language features that depend on 3.0 or 3.5 library classes (such as extension methods, but there is a workaround to get those working with 2.0).
I'll say that VS2010 also supports 2.0-only projects too.