SqlProj file fails to build (Invalid nullable value 'Enable' for C# 7.3 Use 8.0) when trying to use Directory.Build.props file in solution

[PureKrome]

👋🏻 Hi folks,

Not sure if this is a bug or a skill issue (e.g. i'm crap).

I'm add a Directory.Build.props file to the root directory in my solution/repo. Works great against my other projects but this single DB project is failing with:

08630: Invalid 'nullable' value: 'Enable' for C# 7.3. Please use language version '8.0' or greater.

I've tried to be 'smart' with my D.B.props file:

<Project>
    <!-- Exclude SQL Database projects by checking OutputType -->
    <PropertyGroup Condition="'$(OutputType)' != 'Database'">
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
    </PropertyGroup>
    
    <!-- Only set TargetFramework for non-MAUI and non-SQL Database projects -->
    <PropertyGroup Condition="'$(UseMaui)' != 'true' AND '$(OutputType)' != 'Database'">
        <TargetFramework>net9.0</TargetFramework>
    </PropertyGroup>
</Project>

but it still errors.

I also tried to converting the old-style .sqlproj to the new SDK style project but I get a similar issue/error. (targetting <Sdk Name="Microsoft.Build.Sql" Version="1.0.0" />

Is this a known problem?