VS Code CSC : error CS1617: Invalid option '7.3' for /langversion

asp.net-core blazor c# visual-studio-code

Question

I downloaded VS 2017 15.7, .NET Core 2.1.2 and Blazor to try it out. It wasn't working in VS 2017 properly and thought I would try through the dotnet cli and VS Code. Instead I was met with the following error:

CSC : error CS1617: Invalid option '7.3' for /langversion.

In VS, it will run the application show "Loading..." and then nothing. Not sure if the two issues are related

dotnet --info returns the following:

.NET Command Line Tools (2.1.300-preview1-008174)

Product Information:
 Version:            2.1.300-preview1-008174
Commit SHA-1 hash:  b8df89a54f

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17666
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.1.300-preview1-008174\

Microsoft .NET Core Shared Framework Host

  Version  : 2.1.0-preview1-26216-03
  Build    : f2c3216183d20416568a4bbf5bb7d153e826f153

Accepted Answer

Your should use the Preview version of VS for trying out Blazor, which is numbered 15.8.x

vs installer

And install the .net core 2.1 RC. 2.1.2 will not cut it.


Popular Answer

I had the same issue (blank screen when running the app in VS, Invalid option '7.3' from CLI) and I just needed to ugrade version of the SDK. Check this using dotnet --info. 2.1.300-preview1 does not work, you seem to need 2.1.300-rc1 which is available from https://www.microsoft.com/net/download/all




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