.NET Core 3.1运行时加载含依赖的控制器程序集问题排查

许久未使用.NET框架开发，如今在ASP.NET Core主机应用中无法运行时加载包含ControllerBase的DLL程序集。具体而言，当控制器DLL无依赖项时一切正常，但在该DLL中使用兼容.NET Core 3.1的Microsoft.Data.SqlClient 5.0.0执行存储过程后出现问题。

我在主机项目的Startup.cs中编写了如下代码尝试加载程序集及其依赖：

private IEnumerable<Assembly> LoadControllerAssemblies(string controllerPath)
{
    
    AssemblyLoadContext.Default.Resolving += (context, name) => {
        string assemblyPath = $"{controllerPath}\\dep\\{name.Name}.dll";
        if (assemblyPath != null)
            return context.LoadFromAssemblyPath(assemblyPath);
        return null;
    };
    

    var assemblies = new List<Assembly>();
    //To get the location the assembly normally resides on disk or the install directory
    string path = System.Reflection.Assembly.GetExecutingAssembly().CodeBase;

    //once you have the path you get the directory with:
    var directory = Path.Combine(System.IO.Path.GetDirectoryName(path), controllerPath).Replace("file:\\", @"");

    // Carica tutti i file DLL nella cartella specificata
    var dllFiles = Directory.GetFiles(directory, "*.dll");
    foreach (var dllFile in dllFiles)
    {
        try
        {
            // Carica l'assembly con l'API AssemblyLoadContext
            var assembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(dllFile);
            assemblies.Add(assembly);
        }
        catch (Exception ex)
        {
//                    _logger.LogError(ex, $"Errore durante il caricamento dell'assembly {dllFile}");
        }
    }

    //var assemblyPath = Path.Combine(System.IO.Path.GetDirectoryName(path), controllerPath, "dep", "Microsoft.Data.SqlClient.dll").Replace("file:\\", @"");
    //var assemblyDep = AssemblyLoadContext.Default.LoadFromAssemblyPath(assemblyPath);

    return assemblies;
}

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    //string path = System.Reflection.Assembly.GetExecutingAssembly().Location;
    services.AddHttpContextAccessor();


    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_3_0);

    var controllerAssemblies = LoadControllerAssemblies("Controllers");

    // Registra i controller di API con il framework DI
    foreach (var assembly in controllerAssemblies)
    {

        services.AddMvc()
          .AddApplicationPart(assembly).AddControllersAsServices();
    }
    
    
    services.AddHttpClient("apiClient", client => {
        client.BaseAddress = new Uri(Globals.SL_URI);
    }).ConfigurePrimaryHttpMessageHandler(() => {
        var handler = new HttpClientHandler();
        handler.ServerCertificateCustomValidationCallback = (message, certificate, chain, errors) => true;
        return handler;
    });



    services.AddRouting();

    //services.AddHostedService<ControllerLoader>();
}

尝试多种方案均失败：

• 将Microsoft.Data.SqlClient放在依赖文件夹加载时，抛出System.Reflection.ReflectionTypeLoadException，提示无法加载该程序集，参数错误；
• 将所有依赖与控制器DLL放在同一目录时，应用可启动，但调用API时提示“Microsoft.Data.SqlClient is not supported on this platform.”；

仅有的可行方案是在主项目中引入Microsoft.Data.SqlClient依赖，但这违背了控制器模块可独立开发无需修改主项目的初衷。

请问问题出在哪里？是否与.NET Core 3.1版本有关？还有哪些可尝试的解决办法？

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