Azure Functions运行时找不到已部署DLL的原因咨询

问题描述 #

部署Azure Function后遇到以下运行时错误：

Microsoft.Azure.WebJobs.Script: Error building configuration in an external startup class.
System.Private.CoreLib: Could not load file or assembly ', Version=1.0.0.0,
Culture=neutral, PublicKeyToken=null'.

部署已成功，且在App Files中能看到该DLL。环境为C#/.NET 6.0、Functions v4.0，通过Deployment Center生成的GitHub Workflow Action部署。

相关配置信息 #

项目包引用 #

<ItemGroup>
  <PackageReference Include="Azure.Identity" Version="1.8.2" />
  <PackageReference Include="Azure.Security.KeyVault.Secrets" Version="4.5.0" />
  <PackageReference Include="Azure.Storage.Blobs" Version="12.15.1" />
  <PackageReference Include="Cosmonaut" Version="2.11.3" />
  <PackageReference Include="Cosmonaut.ApplicationInsights" Version="2.1.1" />
  <PackageReference Include="Cosmonaut.Extensions.Microsoft.DependencyInjection" Version="2.3.0" />
  <PackageReference Include="Cosmonaut.NestedQueries" Version="2.11.4" />
  <PackageReference Include="Microsoft.Azure.AppConfiguration.AspNetCore" Version="6.0.0" />
  <PackageReference Include="Microsoft.Azure.Functions.Extensions" Version="1.1.0" />
  <PackageReference Include="Microsoft.Azure.Services.AppAuthentication" Version="1.6.2" />
  <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.SendGrid" Version="3.0.3" />
  <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.Storage" Version="5.1.1" />
  <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="7.0.1">
    <PrivateAssets>all</PrivateAssets>
    <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
  </PackageReference>
  <PackageReference Include="Microsoft.Extensions.Azure" Version="1.6.3" />
  <PackageReference Include="Microsoft.Extensions.Hosting" Version="7.0.1" />
  <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.1.3" />
</ItemGroup>

GitHub Action部署脚本 #

# Docs for the Azure Web Apps Deploy action: https://github.com/azure/functions-action
# More GitHub Actions for Azure: https://github.com/Azure/actions

name: Build and deploy dotnet core app to Azure Function App - brokentoysapi3

on:
  push:
    branches:
      - master
  workflow_dispatch:

env:
  AZURE_FUNCTIONAPP_PACKAGE_PATH: './api/_new/BrokenToys.Api/' # set this to the path to your web app project, defaults to the repository root
  DOTNET_VERSION: '6.0.x' # set this to the dotnet version to use

jobs:
  build-and-deploy:
    runs-on: windows-latest
    steps:
      - name: 'Checkout GitHub Action'
        uses: actions/checkout@v2

      - name: Setup DotNet ${{ env.DOTNET_VERSION }} Environment
        uses: actions/setup-dotnet@v1
        with:
          dotnet-version: ${{ env.DOTNET_VERSION }}

      - name: 'Resolve Project Dependencies Using Dotnet'
        shell: pwsh
        run: |
          pushd './${{ env.AZURE_FUNCTIONAPP_PACKAGE_PATH }}'
          dotnet build --configuration Release --output ./output
          popd

      - name: 'Run Azure Functions Action'
        uses: Azure/functions-action@v1
        id: fa
        with:
          app-name: 'brokentoysapi3'
          slot-name: 'Production'
          package: '${{ env.AZURE_FUNCTIONAPP_PACKAGE_PATH }}/output'
          publish-profile: ${{ secrets.AZUREAPPSERVICE_PUBLISHPROFILE_E20EFE8EF7D84C4AA5B5C75BE0B66D0F }}

Startup类代码 #

using BrokenToys.Api.Models.Games;
using Cosmonaut;
using Cosmonaut.Extensions.Microsoft.DependencyInjection;
using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Extensions.Configuration;

[assembly: FunctionsStartup(typeof(BrokenToys.Api.Startup))]

namespace BrokenToys.Api
{
    public class Startup : FunctionsStartup
    {
        public static IConfiguration Configuration { set; get; }


        public override void Configure(IFunctionsHostBuilder builder)
        {
 
            var cosmosSettings = 
                    new CosmosStoreSettings
                    ("BrokenToys", "https://<mycosmosdb>.documents.azure.com:443/", "<mykey>");

            builder.Services.AddCosmosStore<Score>(cosmosSettings);
            builder.Services.AddCosmosStore<Player>(cosmosSettings);

        }
    }
}

可能的原因及解决方法 #

• 构建输出目录结构问题：GitHub Action中使用dotnet build输出到./output，但Azure Functions运行时期望DLL位于站点根目录或正确的子目录。build命令会保留嵌套目录结构（比如bin/Release/net6.0），导致运行时找不到主程序集。
  解决：改用dotnet publish替代dotnet build，publish命令会将所有依赖和主程序集整理到指定目录的根层级：

  dotnet publish --configuration Release --output ./output
  

• 程序集依赖缺失或版本不匹配：主DLL存在，但它依赖的其他DLL可能缺失、版本不对，或者被错误排除在部署包外。比如Cosmonaut相关包的间接依赖未被正确复制。
  解决：

  1. 本地执行dotnet publish，检查输出目录是否包含所有必要的依赖DLL；
  2. 检查项目文件中是否有PrivateAssets设置导致依赖未被复制；
  3. 升级Microsoft.NET.Sdk.Functions到最新稳定版，确保SDK与Functions Runtime兼容。

• Azure Functions运行时版本不兼容：虽然指定了Functions v4.0，但Azure门户中Function App的运行时版本可能未正确设置为.NET 6。
  解决：

  1. 登录Azure门户，进入Function App；
  2. 在配置 > 常规设置中，确认运行时版本设置为.NET 6 (Isolated)或.NET 6 (In-process)（根据项目模式选择）。

• Startup类加载问题：错误提示提到Error building configuration in an external startup class，说明Startup类加载时出错，可能是引用的程序集缺失，或者命名空间、类名配置错误。
  解决：

  1. 确认[assembly: FunctionsStartup(typeof(BrokenToys.Api.Startup))]中的命名空间和类名完全正确；
  2. 检查Startup类中引用的BrokenToys.Api.Models.Games等本地项目是否已被正确构建并包含在部署包中。

• 部署包文件权限问题：少数情况下，部署后的DLL文件权限不足，导致运行时无法读取。
  解决：在Azure门户的Function App中，进入高级工具 > Kudu，打开CMD或PowerShell，检查站点wwwroot目录下的DLL文件权限，确保IIS AppPool用户有读取权限。

内容的提问来源于stack exchange，提问作者Jeffrey Meyer