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首页 > 解决方案 > 无法让 Lamar (IOC) 解决 .NET Core 3.1 中的 API 控制器依赖关系

c# - 无法让 Lamar (IOC) 解决 .NET Core 3.1 中的 API 控制器依赖关系

问题描述

尝试使用 Lamar 调用下面的控制器以在运行时解决依赖关系时出现错误。

我已经尝试过.AddControllersAsServices()，但仍然得到相同的结果。

使用

Container.GetInstance<IDataAccess>()在监视窗口内工作，但不会在运行时解析

Container.WhatDoIHave()也表明存在依赖关系

问题？
我在 Lamar 配置中缺少什么来解析控制器？

[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
    private readonly IDataAccess _dataAccess;
    private readonly ILogger<WeatherForecastController> _logger;

    public WeatherForecastController(IDataAccess dataAccess, ILogger<WeatherForecastController> logger)
    {
        _dataAccess = dataAccess;
    }

    [HttpGet]
    public IEnumerable<string> Get()
    {
        return _dataAccess.GetAll();
    }
}

启动.cs


public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public IContainer Container { get; private set; }

    public void ConfigureContainer(ServiceRegistry services)
    {
        Container = new Container(cfg =>
        {
            cfg.Scan(scanner =>
            {
                scanner.AssembliesAndExecutablesFromApplicationBaseDirectory(a =>
                    a.FullName.Contains("Test3.1"));
                scanner.WithDefaultConventions();
                scanner.SingleImplementationsOfInterface();
            });
        });

        services
            .AddControllers(options =>
            {
                // Disable automatic fallback to JSON
                options.ReturnHttpNotAcceptable = true;

                // Honor browser's Accept header (e.g. Chrome)
                options.RespectBrowserAcceptHeader = true;
            })
            .AddControllersAsServices();

        services.AddMvc()
            .AddControllersAsServices();

        Container.WhatDidIScan();
        Container.WhatDoIHave();

        Console.Write("Container Instantiated");
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();
        app.UseDefaultFiles();
        app.UseStaticFiles();
        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

程序.cs


public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .UseLamar()
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder
                    .UseContentRoot(Directory.GetCurrentDirectory())
                    .UseIISIntegration()
                    .UseStartup<Startup>();

            });
}

处理请求时发生未处理的异常。

LamarException：无法构建'Test3._1.Controllers.WeatherForecastController'的注册实例weatherForecastController：无法填充任何公共构造函数的依赖关系可用构造函数：new WeatherForecastController（IDataAccess dataAccess，ILogger<Test3._1.Controllers.WeatherForecastController>logger）* IDataAccess未在此容器中注册，不能任何缺失的家庭政策自动发现

标签： c#dependency-injectionstructuremap.net-core-3.1lamar

解决方案

错误消息表明容器无法解析控制器的依赖关系。确保这些依赖项已在容器中注册，以便它知道在激活控制器时如何解决它们。

这是因为正在配置单独的容器，Startup而框架使用的容器并不知道，IDataAccess因为它Scan没有应用于其容器。

参考Lamar - 与 ASP.Net Core 集成

public class Startup {

    public Startup(IConfiguration configuration) {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    //REMOVED IContainer. It is not needed

    public void ConfigureContainer(ServiceRegistry services) {

        //Apply scan to the registry used by framework so container is aware of types.
        services.Scan(scanner => {
            scanner.AssembliesAndExecutablesFromApplicationBaseDirectory(a =>
                a.FullName.Contains("Test3.1"));
            scanner.WithDefaultConventions();
            scanner.SingleImplementationsOfInterface();
        });

        services
            .AddControllers(options => {
                // Disable automatic fallback to JSON
                options.ReturnHttpNotAcceptable = true;
                // Honor browser's Accept header (e.g. Chrome)
                options.RespectBrowserAcceptHeader = true;
            })
            .AddControllersAsServices();

        services.AddMvc()
            .AddControllersAsServices();

        services.WhatDidIScan();
        services.WhatDoIHave();

        Console.Write("Container Instantiated");
    }

    //...omitted for brevity
}

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