Slow Build Times in .NET Core 3.1 and 5.0

Question

I've noticed that the build time is exponentially slower in my new .NET Core project than in previous projects written in .NET Standard 4. I tried a number of other solutions mentioned on here to no avail.

Answer 1

I had a "eureka" moment and finally tracked down the problem to having enabled nullable reference types in the project (.csproj) file.

<PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
    <Nullable>enable</Nullable>
    <Configurations>Debug;Release;Stage</Configurations>
</PropertyGroup>

I didn't want to disable the feature but I also don't need my build times taking minutes instead of seconds. To workaround this issue, I added a condition to my .csproj file to set nullability to false when performing a debug build inside Visual Studio:

<PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
    <Nullable>enable</Nullable>
    <Configurations>Debug;Release;Stage</Configurations>
</PropertyGroup>

<!-- Disable nullable checks on debug build (fixes slow build issue) -->
<Target Name="DisableNullableForVisualStudioBuild"
        BeforeTargets="CoreCompile"
        Condition="'$(BuildingInsideVisualStudio)' == 'True' And '$(BuildingProject)' == 'True' And '$(Configuration)' == 'Debug'">
    <PropertyGroup>
        <Nullable>disable</Nullable>
    </PropertyGroup>
</Target>

Voila, problem solved! This of course does have the unfortunate side effect of not having the compiler provide me warnings inside the Output panel regarding nullables, but I still get Intellisense warnings in real-time, so for me it's an acceptable compromise.