尝试在 WebApi（Net Framework）中使用 IoC 容器时出错

Question

我正在尝试在 WebApi 模板中使用 IoC 容器。我创建了一个空的 Web App Framework 项目，并选择使用 WebApi。然后我添加了 Unity NuGet 包并将以下内容添加到 Application_Start:

protected void Application_Start()
{
    GlobalConfiguration.Configure(WebApiConfig.Register);
    UnityConfig.Register();
}

UnityConfig：

public class UnityConfig
{
    public static UnityContainer Register()
    {
        var container = new UnityContainer();
        container.RegisterType<IMyClass, MyClass>();

        GlobalConfiguration.Configuration.DependencyResolver = new UnityResolver(container);

        return container;
    }

}

我的 UnityResolver 在这里（代码大部分是抄袭的，但看起来很标准）：

public class UnityResolver : IDependencyResolver
{
    protected IUnityContainer container;

    public UnityResolver(IUnityContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        this.container = container;
    }

    public object GetService(Type serviceType)
    {
        try
        {
            return container.Resolve(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return null;
        }
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        try
        {
            return container.ResolveAll(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return new List<object>();
        }
    }

    public IDependencyScope BeginScope()
    {
        var child = container.CreateChildContainer();
        return new UnityResolver(child);
    }

    public void Dispose()
    {
        Dispose(true);
    }

    protected virtual void Dispose(bool disposing)
    {
        container.Dispose();
    }
}

当我现在运行这个时，我得到以下错误：

Unity.Exceptions.ResolutionFailedException: 'Resolution of the dependency failed, type = 'System.Web.Http.Hosting.IHostBufferPolicySelector', name = '(none)'. Exception occurred while: while resolving. Exception is: InvalidOperationException - The current type, System.Web.Http.Hosting.IHostBufferPolicySelector, is an interface and cannot be constructed. Are you missing a type mapping? ----------------------------------------------- At the time of the exception, the container was: Resolving System.Web.Http.Hosting.IHostBufferPolicySelector,(none) '

很明显，在告诉它我想使用哪个 IoC 库之后，我需要注入一些内部依赖项，或者告诉它，或者更早（或更晚）注册它。

Answer 1

Clearly, after telling it which IoC library I want to use, I need to inject some internal dependencies, or tell it to, or perhaps, register this earlier (or later).

没错。您需要注册所有将通过 Unity 解析的类型。报错提示你缺少IHostBufferPolicySelector，所以你需要注册

public static UnityContainer Register()
{
    var container = new UnityContainer();

    // Register all types with Unity here
    container.RegisterType<IHostBufferPolicySelector, OwinBufferPolicySelector>();

    GlobalConfiguration.Configuration.DependencyResolver = new UnityResolver(container);

    return container;
}

我不确定 OwinBufferPolicySelector 是否是你需要的，因为你没有提供足够的信息，但你确实需要为它映射一个实现（可能还有几个其他接口）命令继续。

如评论中所述，如果您安装一个预制的 Unity 包（例如 Unity.WebAPI）来提供此实现，可能会更容易。

如果您遵循 Dependency Injection in ASP.NET Web API 2 文档，它也会有很大帮助。

尝试在 WebApi（Net Framework）中使用 IoC 容器时出错

Error while trying to use an IoC container inside WebApi (Net Framework)

c#

web-applications

inversion-of-control

unity-container

asp.net-web-api