Blazor WASM项目升级到netcoreapp3.1后找不到BlazorWebAssembly JS文件报错

你遇到的Unable to find BlazorWebAssembly JS files. This usually indicates a packaging error报错，核心原因是.NET Core 3.1版本的Blazor WASM框架规则和你修改后的项目配置不匹配，具体修复步骤如下：

• 修正项目SDK配置：.NET Core 3.1 版本的Blazor WASM还没有推出独立的Microsoft.NET.Sdk.BlazorWebAssembly SDK，该专属SDK是.NET 5及之后版本才支持的，你需要把项目的Sdk属性改回原来的Microsoft.NET.Sdk.Web
• 补充Blazor WASM标识：在PropertyGroup节点中新增<BlazorWebAssembly>true</BlazorWebAssembly>配置，告知打包工具这是Blazor WASM项目
• 恢复缺失的配置项：把你修改时删掉的两个项目引用、logo.png静态资源复制配置加回项目文件，依赖缺失也会导致打包流程中断无法生成JS文件
• 补充3.1版本专属NuGet引用：在ItemGroup中新增Blazor WASM 3.2版本（对应.NET Core 3.1的最后稳定发行版）的必备依赖：

<PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="3.2.1" />
<PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Build" Version="3.2.1" PrivateAssets="all" />
<PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="3.2.1" PrivateAssets="all" />

• 重新生成项目：保存修改后的项目文件，删除解决方案所有项目的bin、obj文件夹，执行dotnet restore后重新生成项目即可解决报错

修复后完整项目文件参考 #

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <RazorLangVersion>3.0</RazorLangVersion>
    <BlazorWebAssembly>true</BlazorWebAssembly>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
  </PropertyGroup>
  <ItemGroup>
    <None Remove="Resources\bg-BG.yml" />
    <None Remove="Resources\en-US.yml" />
  </ItemGroup>
  <ItemGroup>
    <ProjectReference Include="..\..\BlazorShop.Common\BlazorShop.Common.csproj" />
    <ProjectReference Include="..\..\BlazorShop.Models\BlazorShop.Models.csproj" />
  </ItemGroup>
  <ItemGroup>
    <Content Update="wwwroot\logo.png">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </Content>
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="3.2.1" />
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Build" Version="3.2.1" PrivateAssets="all" />
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="3.2.1" PrivateAssets="all" />
  </ItemGroup>
  <ItemGroup>
    <Folder Include="Pages\Admin\Fills\" />
    <Folder Include="Pages\Admin\Ingredients\" />
    <Folder Include="Pages\Admin\Bases\" />
    <Folder Include="Pages\Admin\Orders\" />
  </ItemGroup>
</Project>

内容的提问来源于stack exchange，提问作者Vladimir Petukhov