title: VS Code CSC : error CS1617: Invalid option '7.3' for /langversion
body: <p>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:</p>
  
  <p><code>CSC : error CS1617: Invalid option '7.3' for /langversion.</code></p>
  
  <p>In VS, it will run the application show "Loading..." and then nothing. Not sure if the two issues are related</p>
  
  <p><code>dotnet --info</code> returns the following:</p>
  
  <pre class="lang-none prettyprint-override"><code>.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
  </code></pre>