没有无参数构造函数定义了Hangfire Ninject

Question

我在激活类的实例时遇到了问题，没有定义任何非参数构造函数。

构造函数：

public HangfireExecutor(ICommandDispatcher commandDispatcher, IQueryDispatcher queryDispatcher, IMapper mapper)

如何注册和配置Hangfire (使用三个点而不是敏感信息)：

[assembly: OwinStartupAttribute(typeof(Web2.Startup))]
    public partial class Startup

    private IAppBuilder _app;
    public void Configuration(IAppBuilder app)
    {
        ConfigureAuth(app);
        _app = app;

        GlobalConfiguration.Configuration.UseSqlServerStorage("...");

        _app.UseHangfireDashboard("/...", new DashboardOptions
        {
            Authorization = new[] { new HangfireDashboardAuthorizationFilter() },
            AppPath = "/Identity/Create"
        });

        _app.UseHangfireServer();

        _app.UseNinjectMiddleware(CreateKernel);
    }

在IoC容器中注册：

public partial class Startup
{
...
protected IKernel CreateKernel()
{
    var kernel = new StandardKernel();
    ...
    kernel.Bind<HangfireExecutor>().ToSelf().InBackgroundJobScope();
    GlobalConfiguration.Configuration.UseNinjectActivator(kernel);
    return kernel;

错误：

System.MissingMethodException
No parameterless constructor defined for this object hangfire ninject System.RuntimeTypeHandle.CreateInstance
System.MissingMethodException: No parameterless constructor defined for this object
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
at System.Activator.CreateInstance(Type type, Boolean nonPublic)
at System.Activator.CreateInstance(Type type)
at Hangfire.JobActivator.ActivateJob(Type jobType)
at Hangfire.JobActivator.SimpleJobActivatorScope.Resolve(Type type)
at Hangfire.Server.CoreBackgroundJobPerformer.Perform(PerformContext context)

对我来说，Hangfire似乎不使用Ninject激活器(?)但我不知道为什么。

我学习了两个教程:关于Hangfire站点和Hangfire.Ninject github，以及几个github repos等等问题。

对其他未被Hangfire使用的类进行统计，效果良好；使用无参数构造函数安装Hangfire执行器也能正常工作。

我在用：

• ASP .NET MVC 5
• .NET框架4.6.1，
• Hangfire 1.6.21
• Hangfire.Ninject 1.2

Answer 1

由于方法_app.UseNinjectMiddleware(CreateKernel);不创建内核(只保留对metod的委托，创建内核)，在我的示例中，Hangfire配置中正确的命令顺序应该是：

public void Configuration(IAppBuilder app)
    {
        ConfigureAuth(app);
        _app = app;

        GlobalConfiguration.Configuration.UseSqlServerStorage("...");

        _app.UseHangfireDashboard("/...", new DashboardOptions
        {
            Authorization = new[] { new HangfireDashboardAuthorizationFilter() },
            AppPath = "/Identity/Create"
        });

        _app.UseNinjectMiddleware(CreateKernel);
    }

然后在CreateKernel方法的末尾：

kernel.Bind<HangfireExecutor>().ToSelf().InBackgroundJobScope();

        GlobalConfiguration.Configuration.UseNinjectActivator(kernel);

        _app.UseHangfireServer();

        return kernel;

现在，Hangfire开始解决依赖关系。我认为在启动应用程序后尽快创建内核是很重要的，否则Hangfire可能不会被初始化，后台作业也不会被执行。