WebAPI 中使用 Ninject

尝试在WebApi中使用Ninject进行依赖注入

public class AdminController : ApiController
    {
        [Inject]
        public IAdminService AdminService { get; set; }

        // GET api/admin
        public IEnumerable<Admin> Get()
        {
            return AdminService.Admins();
            //return new string[] { "value1", "value2" };
        }

    }

结果运行出错，提示NullReferenceException

在网上有查询到一篇博文 http://wildermuth.com/2012/02/26/WebAPI_and_Ninject

先用NuGet安装CommonServiceLocator.NinjectAdapter

修改App_Start下NinjectWebCommon.cs文件private static IKernel CreateKernel(){...}代码段

using NinjectAdapter;
 
public static class NinjectMVC3
{
  static readonly Bootstrapper bootstrapper 
    = new Bootstrapper();
 
  public static void Start()
  {
    DynamicModuleUtility.RegisterModule(typeof(OnePerRequestModule));
    DynamicModuleUtility.RegisterModule(typeof(HttpApplicationInitializationModule));
 
    bootstrapper.Initialize(CreateKernel);
 
  }
 
  ...
 
  static IKernel CreateKernel()
  {
    var kernel = new StandardKernel();
 
    // Register Dependencies
    RegisterServices(kernel);
 
    // Set Web API Resolver
    GlobalConfiguration.Configuration
                       .ServiceResolver
                       .SetResolver(new NinjectServiceLocator(kernel));
 
    return kernel;
  }
  ...
}

结果：GlobalConfiguration.Configuration.ServiceResolver.SetResolver(new NinjectServiceLocator(kernel));

在引用System.Web.Http空间名报错，没找到ServiceResolver，只有DependencyResolver。

 

解决方法：

GlobalConfiguration.Configuration.DependencyResolver = new NinjectDependencyResolver(kernel);

        private static IKernel CreateKernel()
        {
            var kernel = new StandardKernel();
            kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
            kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();
            
            RegisterServices(kernel);
            
            // Set Web API Resolver
            GlobalConfiguration.Configuration.DependencyResolver = new NinjectDependencyResolver(kernel);

            return kernel;
        }

 

关于NinjectDependencyResolver这个类代码如下

using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Web.Http.Dependencies;
using Ninject;
using Ninject.Syntax;

namespace WebApiNinject.App_Start
{
    public class NinjectDependencyScope : IDependencyScope
    {
        private IResolutionRoot resolver;

        internal NinjectDependencyScope(IResolutionRoot resolver)
        {
            Contract.Assert(resolver != null);

            this.resolver = resolver;
        }

        public void Dispose()
        {
            IDisposable disposable = resolver as IDisposable;
            if (disposable != null)
                disposable.Dispose();

            resolver = null;
        }

        public object GetService(Type serviceType)
        {
            if (resolver == null)
                throw new ObjectDisposedException("this", "This scope has already been disposed");

            return resolver.TryGet(serviceType);
        }

        public IEnumerable<object> GetServices(Type serviceType)
        {
            if (resolver == null)
                throw new ObjectDisposedException("this", "This scope has already been disposed");

            return resolver.GetAll(serviceType);
        }
    }

    public class NinjectDependencyResolver : NinjectDependencyScope, IDependencyResolver
    {
        private IKernel kernel;

        public NinjectDependencyResolver(IKernel kernel)
            : base(kernel)
        {
            this.kernel = kernel;
        }

        public IDependencyScope BeginScope()
        {
            return new NinjectDependencyScope(kernel.BeginBlock());
        }
    }
}

好了，现在可以在ApiController中使用Ninject了。