使用 MVVMLight 时如何设置 Web API DependencyResolver

Question

我正在使用 OWIN 在使用 galasoft mvvmlight 框架的 wpf 桌面应用程序中自行托管 Web api Web 服务。当我尝试将我的模型数据服务之一依赖注入网络 api 控制器时，我收到有关 "Make sure that the controller has a parameterless public constructor" 的错误。

我知道 Web api 控制器不支持开箱即用的依赖注入。我看过许多示例，详细说明如何在使用 Unity 或编写您自己的时提供自定义 IDependencyResolver。有没有直接的方法来使用 mvvmlight SimpleIoc.Default 设置 Web api 启动 class HttpConfiguration 对象的 DependencyResolver 属性?

作为解决方法，我目前通过在我的 api 控制器构造函数中调用 SimpleIoc.Default.GetInstance() 来设置我的数据服务。这行得通，并且在功能上可能与依赖注入机制相同，但依赖注入似乎更优雅。

public class webApiStartup {
    public void Configuration(IAppBuilder appBuilder)
    {
        // Configure Web API for self-host. 
        HttpConfiguration config = new HttpConfiguration();
        config.Routes.MapHttpRoute(
            name: "FileServerApi",
            routeTemplate: "{controller}/{filename}"
            ,defaults: new { Controller = "filesController" }
        );
//*
//* The Following line of Code does not work. But intellisense suggests
//* that there is a conversion available ?
//*
        config.DependencyResolver = (IDependencyResolver)SimpleIoc.Default;

        appBuilder.UseWebApi(config);
    }
}

//*
//* This constructor for the web api controller works
//* but it is not as elegant as dependency injection
//*
public class filesController : ApiController
{
    ILocalDataService _LocalDataSvc = null;

    public filesController() {
        _LocalDataSvc = SimpleIoc.Default.GetInstance<ILocalDataService>();
    }

Answer 1

演员阵容

 config.DependencyResolver = (IDependencyResolver)SimpleIoc.Default;

将失败，因为 SimpleIoc 不是从 IDependencyResolver.

派生的

为派生自 IDependencyResolver

的容器创建包装器

public class SimpleIocResolver : IDependencyResolver {
    protected ISimpleIoc container;

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

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

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

    public IDependencyScope BeginScope() {
        return new SimpleIocResolver(container);
    }

    public void Dispose() {
        //No Op
    }
}

并在配置时使用它

config.DependencyResolver = new SimpleIocResolver(SimpleIoc.Default);

然后可以重构 ApiController

public class FilesController : ApiController {
    ILocalDataService _LocalDataSvc = null;

    public FilesController(ILocalDataService svc) {
        _LocalDataSvc = svc;
    }

    //...

前提是依赖已经注册到容器中

引用Dependency Injection in ASP.NET Web API 2

使用 MVVMLight 时如何设置 Web API DependencyResolver

How to set Web API DependencyResolver when using MVVMLight

c#

dependency-injection

mvvm

mvvm-light

asp.net-web-api2