Could not load the embedded file manifest 'Microsoft.Extensions.FileProviders.Embedded.Manifest.xml' ASP.NET Core 3.0

If you're migrating from ASP.NET-Core 2.x to 3.x, 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.

Microsoft.Extensions.FileProviders.Embedded needs to be added 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>

For those not migrating from 2.x to 3.x, don't forget to also add the following to your .csproj:

<Project Sdk="Microsoft.NET.Sdk.Web">
    ...
    <PropertyGroup>
        <GenerateEmbeddedFilesManifest>true</GenerateEmbeddedFilesManifest>
    </PropertyGroup>
    ...
    <ItemGroup>
        <EmbeddedResource Include="..." /> <!-- Add your directories and/or files here. -->
    </ItemGroup>
    ...
</Project>