WebJobs 3.0中注入EF Core 7.0上下文失败的问题求助

我正在开发首个使用Entity Framework的WebJob应用，基于.NET 7框架，使用WebJobs 3.0与EF.NET Core 7.0版本。尝试将ApplicationDbContext注入应用构建器时，出现错误：

Cannot bind parameter 'db' to type ApplicationDbContext. Make sure the parameter Type is supported by the binding

网上相关示例因Azure WebJobs版本迭代快，未找到适配当前版本的可行方案。

原代码 #

Program.cs #

class Program
{
    static async Task Main()
    {
        var builder = new HostBuilder();
        builder.ConfigureWebJobs(b =>
        {
            b.AddTimers();
            b.AddAzureStorageCoreServices();
        });
        builder.ConfigureLogging((context, b) =>
        {
            b.AddConsole();
        });
        builder.ConfigureAppConfiguration((hostContext, configApp) =>
         {
             configApp.SetBasePath(Directory.GetCurrentDirectory());
             configApp.AddEnvironmentVariables(prefix: "ASPNETCORE_");
             configApp.AddJsonFile($"appsettings.json", true);
             configApp.AddJsonFile($"appsettings.{hostContext.HostingEnvironment.EnvironmentName}.json", true);

         });
       
       builder.ConfigureServices(services => { services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer("My full connection string"));
            services.AddTransient<IEmailSender, EmailSender>();
                                              });
        var host = builder.Build();
        using (host)
        //{
            await host.RunAsync();
        }
    }
}

public class Functions

public static void Sendemails([TimerTrigger("0 0 20 * * SUN-THU")] TimerInfo timer,
         ILogger logger,  ApplicationDbContext db)

    {
   
  
        var mylist = db.Users.ToList();
    
    }
}

尝试的替代配置方式 #

var serviceCollection = new ServiceCollection();
ConfigureServices(serviceCollection);
     .....

  builder.ConfigureServices((context, sc) =>  sc= serviceCollection);
        var host = builder.Build();
   
        using (host)
        {
            await host.RunAsync();
        } 
}
 .....

    private void ConfigureServices(IServiceCollection services)
{
   
    services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(_configuration.GetConnectionString("DefaultConnection")))
           
    }

项目文件 (.csproj) #

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

  <PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net7.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <None Remove="appsettings.Development.json" />
    <None Remove="appsettings.json" />
  </ItemGroup>

  <ItemGroup>
    <Content Include="appsettings.Development.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <ExcludeFromSingleFile>true</ExcludeFromSingleFile>
      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
    </Content>
    <Content Include="appsettings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <ExcludeFromSingleFile>true</ExcludeFromSingleFile>
      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
    </Content>
  </ItemGroup>

  <ItemGroup>
    <PackageReference 
Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="7.0.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs" Version="3.0.33" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions" Version="4.0.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.OpenApi.Configuration.AppSettings" Version="1.5.0" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.SendGrid" Version="3.0.2" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.Storage" Version="5.0.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="7.0.1" />
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="7.0.0" />
    <PackageReference Include="Microsoft.Extensions.Logging" Version="7.0.0" />
    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="7.0.0" />
    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="7.0.0" />
    <PackageReference Include="SendGrid" Version="9.28.1" />
  </ItemGroup>

</Project>

错误核心原因：

1. WebJobs仅支持预定义类型（如TimerInfo、ILogger）直接作为方法参数绑定，自定义服务（如ApplicationDbContext）无法直接注入方法参数。
2. 静态类/静态方法无法利用DI容器实例化，无法注入依赖。

1. 修改Functions类为非静态，通过构造函数注入依赖 #

将作业类改为非静态，通过构造函数接收依赖：

public class Functions
{
    private readonly ApplicationDbContext _db;
    private readonly ILogger<Functions> _logger;

    // 构造函数注入依赖
    public Functions(ApplicationDbContext db, ILogger<Functions> logger)
    {
        _db = db;
        _logger = logger;
    }

    public void Sendemails([TimerTrigger("0 0 20 * * SUN-THU")] TimerInfo timer)
    {
        var mylist = _db.Users.ToList();
        _logger.LogInformation($"查询到{mylist.Count}个用户");
    }
}

2. 修正Program.cs的服务配置 #

保留原有配置逻辑，优化连接字符串读取方式，并注册作业类到DI容器：

class Program
{
    static async Task Main()
    {
        var builder = new HostBuilder();
        builder.ConfigureWebJobs(b =>
        {
            b.AddTimers();
            b.AddAzureStorageCoreServices();
        });
        builder.ConfigureLogging((context, b) =>
        {
            b.AddConsole();
        });
        builder.ConfigureAppConfiguration((hostContext, configApp) =>
        {
            configApp.SetBasePath(Directory.GetCurrentDirectory());
            configApp.AddEnvironmentVariables(prefix: "ASPNETCORE_");
            configApp.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
            configApp.AddJsonFile($"appsettings.{hostContext.HostingEnvironment.EnvironmentName}.json", optional: true, reloadOnChange: true);
        });
       
        builder.ConfigureServices((context, services) => 
        {
            // 从配置文件读取连接字符串
            var connectionString = context.Configuration.GetConnectionString("DefaultConnection");
            services.AddDbContext<ApplicationDbContext>(options => 
                options.UseSqlServer(connectionString));
            services.AddTransient<IEmailSender, EmailSender>();
            // 注册作业类，WebJobs运行时会自动实例化
            services.AddTransient<Functions>();
        });

        var host = builder.Build();
        using (host)
        {
            await host.RunAsync();
        }
    }
}

3. 修正替代配置方式（可选） #

若使用独立的ConfigureServices方法，需将自定义服务集合合并到WebJobs的服务容器，而非直接赋值：

static async Task Main()
{
    var builder = new HostBuilder();
    // ... 其他配置 ...

    builder.ConfigureServices((context, sc) => 
    {
        var serviceCollection = new ServiceCollection();
        ConfigureServices(serviceCollection, context.Configuration);
        // 合并服务到WebJobs容器
        foreach (var service in serviceCollection)
        {
            sc.Add(service);
        }
    });

    var host = builder.Build();
    using (host)
    {
        await host.RunAsync();
    }
}

private static void ConfigureServices(IServiceCollection services, IConfiguration configuration)
{
    var connectionString = configuration.GetConnectionString("DefaultConnection");
    services.AddDbContext<ApplicationDbContext>(options => 
        options.UseSqlServer(connectionString));
    services.AddTransient<IEmailSender, EmailSender>();
    services.AddTransient<Functions>();
}

关键补充 #

确保appsettings.json中配置连接字符串：

{
  "ConnectionStrings": {
    "DefaultConnection": "你的SQL Server连接字符串"
  }
}

内容的提问来源于stack exchange，提问作者Haim Katz