Csproj file with support for compiling scss files with dotnet watch.

BlazorScssDemoFinal.csproj

<Project Sdk="Microsoft.NET.Sdk.BlazorWebAssembly">

  <PropertyGroup>
    <TargetFramework>net5</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="5.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="5.0.0" PrivateAssets="all" />
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Authentication" Version="5.0.0" />
    <PackageReference Include="Microsoft.Extensions.Http" Version="5.0.0" />
    <PackageReference Include="System.Net.Http.Json" Version="5.0.0" />
  </ItemGroup>

  <!-- Add SCSS files to dotnet watch -->
  <ItemGroup>
    <Watch Include="**\*.scss" />
    <None Update="**\*.css" watch="false" />
  </ItemGroup>

  <!-- Compile SCSS files into CSS -->
  <ItemGroup>
    <ComponentScssFiles Include="**/*/*.scss" Exclude="node_modules/**;wwwroot/**;Styles/**" />
  </ItemGroup>

  <Target Name="CompileComponentSass" BeforeTargets="CompileGlobalSass">
    <Message Text="Compiling Component SCSS files" Importance="high" />
    <Exec Condition="!$([System.Text.RegularExpressions.Regex]::IsMatch('%(ComponentScssFiles.Identity)', `.*[/\\]_.*`))" Command="npm run sass -- --style=compressed --no-source-map --load-path=Styles/Core %(ComponentScssFiles.Identity) %(relativedir)%(filename).css" />
  </Target>

  <Target Name="CompileGlobalSass" BeforeTargets="Compile">
    <Message Text="Compiling global SCSS file" Importance="high" />
    <Exec Command="npm run sass -- --style=compressed Styles:wwwroot/css" />
  </Target>
</Project>