Aspnetcore: error CS1617: Invalid option '7.3' for /langversion

[timnazar]

precious:~ timnazar$ dotnet new blazor -o thoughts
The template "Blazor (standalone)" was created successfully.

Processing post-creation actions...
Running 'dotnet restore' on thoughts/thoughts.csproj...
  Restoring packages for /Users/timnazar/thoughts/thoughts.csproj...
  Restore completed in 168.01 ms for /Users/timnazar/thoughts/thoughts.csproj.
  Generating MSBuild file /Users/timnazar/thoughts/obj/thoughts.csproj.nuget.g.props.
  Generating MSBuild file /Users/timnazar/thoughts/obj/thoughts.csproj.nuget.g.targets.
  Restore completed in 465.43 ms for /Users/timnazar/thoughts/thoughts.csproj.

Restore succeeded.

precious:~ timnazar$ cd thoughts
precious:thoughts timnazar$ dotnet run
CSC : error CS1617: Invalid option '7.3' for /langversion. Use '/langversion:?' to list supported values. [/Users/timnazar/thoughts/thoughts.csproj]

The build failed. Please fix the build errors and run again.

The newly created project is failed on compiling. what's wrong?

.net core version: 2.1.4
os: macOS 10.13.4

[vertonghenb]

I had the same issue and believe it's an issue in VS for mac since they're not supporting C# 7.3 (yet). Try running it from the terminal, that should work. The support for vs for mac is tracked here: aspnet/AspNetCore#5490

[timnazar]

i'm running from the terminal :C

[danroth27]

precious:thoughts timnazar$ dotnet --version
2.1.4

You need to install the .NET Core 2.1 SDK.

[danroth27]

@timnazar We've actually seen quite a few people run into this issue where they don't have the required .NET Core SDK version installed. We're trying to figure out how we can make this requirement clearer. Can you share any details about how you might have missed this step? Which installation steps were you following? Was anything missing or unclear?

[timnazar]

ty, danroth27

[timnazar]

@danroth27 I used the old version in my projects.
in getting started from blazor's page I ran command dotnet new -i Microsoft.AspNetCore.Blazor.Templates

and downloaded templates but not updated .Net.
templates successfully downloaded but not asked or warned to update .Net

[rolandh]

I installed net core 2.1 and it broke net framework 2.0 and also stopped any compiler newer than 7.0 from working. I can select 7.3 but I get this error when trying to build with it. I believe it is the net core installer that is breaking this.

[danroth27]

@rolandh Is it just Blazor apps that are broken or any .NET Core app? If it's the later, you should probably report your issue on https://github.com/dotnet/sdk/issues.