Since ASP.NET-Core 3.0 and above, `Microsoft.NET.Sdk.Web` MSBuild SDK doesn't automatically include `Microsoft.Extensions.FileProviders.Embedded` NuGet package anymore. I had to add `Microsoft.Extensions.FileProviders.Embedded` explicitly. <Project Sdk="Microsoft.NET.Sdk.Web"> ... <ItemGroup> <PackageReference Include="Microsoft.Extensions.FileProviders.Embedded" Version="3.0.3" /> <!-- Or use version 3.1.2 for ASP.NET-Core 3.1 --> </ItemGroup> ... </Project>