是否有可能有多个依赖解析器在ASP.NET MVC 3？ [英] Is it possible to have multiple dependency resolvers in ASP.NET MVC 3?

问题描述

是否有可能有一个以上的依赖解析器在ASP.NET MVC 3（类似于ModelBinders和供应商的情况下）？

Is it possible to have more than one dependency resolver in ASP.NET MVC 3 (similar to the case of ModelBinders and Providers)?

推荐答案

有是我能想到的，其中有多个'集装箱'或'解析器'是非常有用的一个场景，那就是多租户。随着多租户运行在同一个Web应用程序多个客户（组织，用自己的用户群），以及动态的基础上登录切换，请求信息或域信息。

There is one scenario that I could think of where having multiple 'containers' or 'resolvers' is useful and that is multi-tenancy. With multi tenancy you run multiple customers (organizations, with their own set of users) in the same web application, and dynamically switch based on the login, request info, or domain info.

不过， DependencyResolver.Current 是-as达林noted-静态的，所以有可以（或应该做这个），什么都没有。但是，你可以躲在一个的IDependencyResolver 抽象多个集装箱，并返回基于某些条件的实现。它可能是这样的：

Still, DependencyResolver.Current is -as Darin noted- static, so there's nothing you can (or should do about this). However, you could hide multiple containers behind a single IDependencyResolver abstraction and return an implementation based on some criteria. It might look like this:

public class MultiTenantDependencyResolver 
    : IDependencyResolver
{
    Func<int> tenantIdSelector,;
    IDictionary<int, IDependencyResolver> tenantResolvers;

    public MultiTenantDependencyResolver(
        Func<int> tenantIdSelector,
        IDictionary<int, IDependencyResolver> tenantResolvers)
    {
        this.tenantIdSelector = tenantIdSelector;
        this.tenantResolvers= tenantResolvers;
    }

    private IDependencyResolver CurrentResolver
    { 
        get { return this.tenantResolvers[tenantIdSelector()]; }
    }

    public object GetService(Type serviceType)
    {
        return this.CurrentResolver.GetService(serviceType);
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        return this.CurrentResolver.GetAllInstances(serviceType);
    }
}

以下code片段显示了这种用法 MultiTenantDependencyResolver ：

var tenantResolvers = new Dictionary<int, IDependencyResolver>
{
    { Tenants.AbcId, BuildResolver(RegisterForTenantAbc) },
    { Tenants.KlmId, BuildResolver(RegisterForTenantKlm) },
    { Tenants.XyzId, BuildResolver(RegisterForTenantXyz) },
};

var multiTenantResolver = new MultiTenantResolver(
    () => GetTenantIdFromUrl(), tenantResolvers);

DependencyResolver.SetResolver(multiTenantResolver);


private static int GetTenantIdFromUrl()
{
    // TODO: return tenant id
}

private static IDependencyResolver BuildResolver(
    Action<IKernel> tenantSpecificRegistrations)
{
    var kernel = new Kernel();

    // TODO: Tenant agnostic registrations. For instance
    kernel.Bind<ITimeProvider>().To<SystemTimeProvider>();

    tenantSpecificRegistrations(kernel);

    return new NinjectDependencyResolver(kernel);
}

private static void RegisterForTenantAbc(IKernel kernel)
{
    // TODO: regisrations for ABC tenant. For instance
    kernel.Bind<ILogger>().To<AbcTenantLogger>();
}

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