Autofac和的WebAPI - 默认的构造错误 [英] Autofac and WebAPI - Default constructor error

问题描述

我有一个web表单的项目，但现在用的WebAPI的Web服务。我想实现Autofac。我越来越：

 'myController的'没有默认构造函数
 

据该Autofac文档我有配置正确的，但显然是有问题的。我使用Visual Studio 2010 / .NET 4，这里是我的Application_Start

 私人无效的Application_Start（对象发件人，EventArgs的发送）
{
    //这使得API控制器在一个单独的类库
    GlobalConfiguration.Configuration.Services.Replace（typeof运算（IAssembliesResolver），新AssembliesResolver（））;    GlobalConfiguration.Configuration.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;    //为ELMAH的WebAPI
    GlobalConfiguration.Configuration.Filters.Add（新ElmahHandleErrorApiAttribute（））;    VAR JSON = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
    json.SerializerSettings preserveReferencesHandling = Newtonsoft.Json preserveReferencesHandling.Objects。;
    GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);    VAR建设者=新ContainerBuilder（）;    //注册的DbContext
    builder.RegisterType＆LT; MyDbContext＆GT;（）
        。至于＆LT; IMyDbContext＆GT;（）
        .InstancePerRequest（）;    //注册服务层
    变种businessLayer = Assembly.GetExecutingAssembly（）;
    builder.RegisterAssemblyTypes（AppDomain.CurrentDomain.GetAssemblies（））
        。凡（T =＆GT; t.Name.EndsWith（服务））
        .AsImplementedInterfaces（）;    builder.RegisterApiControllers（Assembly.GetExecutingAssembly（））;
    builder.RegisterWebApiFilterProvider（GlobalConfiguration.Configuration）;    变种容器= builder.Build（）;
    _containerProvider =新ContainerProvider（容器）;    VAR webApiResolver =新AutofacWebApiDependencyResolver（容器）;
    GlobalConfiguration.Configuration.DependencyResolver = webApiResolver;}
 

一个典型的API控制器看起来是这样的：

  [授权]
公共类myController的：ApiController
{
    公共IMyService语境{搞定;组; }    公共myController的（IMyService上下文）
    {
        this.context =背景;
    }    //获取API / dostuff
    ///＆LT;总结＆gt;
    ///获取所有DTOS名单
    ///＆LT; /总结＆gt;
    ///＆LT;＆回报GT;＆LT; /回报＆GT;
    公共IEnumerable的＆LT; MyDto＆GT;得到（）
    {
        尝试
        {
            返回context.MyDtos.ToList（）;
        }
        赶上（异常前）
        {
            VAR消息=的String.Format（{0} {1} HTTP / 1.1 {2}异常：{3}，Request.Method，Request.RequestUri，则httpStatus code.MethodNotAllowed，ex.Message）;
            VAR的errorMessage =新System.Web.Http.HttpError（消息）{{错误code，405}};
            抛出新Htt$p$psponseException(ControllerContext.Request.CreateErrorResponse(HttpStatus$c$c.MethodNotAllowed,错误信息））;
        }
    }
}
 

解决方案

如果你有你的API控制器在不同的装配比你的Web项目，那么你需要需要告诉Autofac凡与长宁找到你的控制器：

  builder.RegisterApiControllers（Assembly.GetExecutingAssembly（））;
 

要

  builder.RegisterApiControllers（typeof运算（myController的）.Assembly）;
 

这将指示Autofac扫描 myController的的组装和注册所有 ApiController 派生类型它所开创那里。

I have a webforms project, but am using WebAPI for web services. I am trying to implement Autofac. I am getting:

'MyController' does not have a default constructor

According to the Autofac documentation I have the configuration correct but obviously there is a problem. I am using Visual Studio 2010/.Net 4. Here is my Application_Start

private void Application_Start(object sender, EventArgs e)
{
    //This enables api controllers in a separate class library
    GlobalConfiguration.Configuration.Services.Replace(typeof(IAssembliesResolver), new AssembliesResolver());

    GlobalConfiguration.Configuration.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;

    //Elmah for webapi
    GlobalConfiguration.Configuration.Filters.Add(new ElmahHandleErrorApiAttribute());

    var json = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
    json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
    GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);

    var builder = new ContainerBuilder();

    //Register DbContext
    builder.RegisterType<MyDbContext>()
        .As<IMyDbContext>()
        .InstancePerRequest();    

    //Register service layer
    var businessLayer = Assembly.GetExecutingAssembly();
    builder.RegisterAssemblyTypes(AppDomain.CurrentDomain.GetAssemblies())
        .Where(t => t.Name.EndsWith("Service"))
        .AsImplementedInterfaces();

    builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
    builder.RegisterWebApiFilterProvider(GlobalConfiguration.Configuration);

    var container = builder.Build();
    _containerProvider = new ContainerProvider(container);

    var webApiResolver = new AutofacWebApiDependencyResolver(container);        
    GlobalConfiguration.Configuration.DependencyResolver = webApiResolver;       

}

A typical api controller looks like this:

 [Authorize]
public class MyController : ApiController
{
    public IMyService context { get; set; }

    public MyController(IMyService context)
    {
        this.context = context;
    }

    // GET api/dostuff
    /// <summary>
    /// Get a list of all dtos
    /// </summary>
    /// <returns></returns>
    public IEnumerable<MyDto> Get()
    {
        try
        {                
            return context.MyDtos.ToList();
        }
        catch (Exception ex)
        {
            var message = string.Format("{0} {1} HTTP/1.1 {2} Exception: {3}", Request.Method, Request.RequestUri, HttpStatusCode.MethodNotAllowed, ex.Message);
            var errorMessage = new System.Web.Http.HttpError(message) { { "ErrorCode", 405 } };
            throw new HttpResponseException(ControllerContext.Request.CreateErrorResponse(HttpStatusCode.MethodNotAllowed, errorMessage));
        }
    }
}

解决方案

If you have your api controllers in a different assembly than your web project, then you need to need to tell Autofac where to find your controllers with changning:

builder.RegisterApiControllers(Assembly.GetExecutingAssembly());

To

builder.RegisterApiControllers(typeof(MyController).Assembly);

This will instruct Autofac to scan the assembly of MyController and register all ApiController derived types what it founds there.

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