Invalid Nullable Value - Enable for C# 7.3

Wednesday, April 22, 2020 → 2 min read

I was playing around with Visual Studio 2019 and the open source ASP.NET Core blog engine Miniblog.Core. I cloned it to my local, opened it in Visual Studio 2019 and tried to build the solution. I immediately ran into the error below:

Error CS8630 Invalid 'nullable' value: 'Enable' for C# 7.3. Please use language version '8.0' or greater.

So, I looked up the error message and every Stack Overflow page I ended up on, says that I have to set the Language Version in Visual Studio. Okay, so how do I do that? I eventually found this answer, which gives you the steps to get to the Advanced Build Settings dialog box for the project.

  • Right-click YourProject, click Properties
  • Click Build if it's not already selected
  • Change Configuration to All Configurations
  • Click Advanced...
  • Change the language version

When the dialog box showed up however, it didn't give me an option to set the Language Version.

Advanced Build Settings

Solution

The solution I ended up with involved manually editing the project file and adding an entry for the Language Version. So, I opened up the Miniblog.Core.csproj file and added <LangVersion>preview</LangVersion> under the <PropertyGroup> settings. It looks like this:

Setting the Language Version manually

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