如何使用fluent API在Kephas注册服务？

Question

我希望保留Kephas提供的DI抽象层，但在我的特殊情况下，我需要注册从第三方库导入的服务。因此，我不能用服务注册所需的[AppServiceContract]属性对服务进行注释。有办法做到这一点吗？

Answer 1

是的有。以下是应采取的步骤：

• 定义一个实现IConventionsRegistrar的类。
• 使用约定构建器注册所需的服务。

样本代码：

public class MyConventionsRegistrar : IConventionsRegistrar
{
    /// <summary>
    /// Registers the conventions.
    /// </summary>
    /// <param name="builder">The registration builder.</param>
    /// <param name="candidateTypes">The candidate types which can take part in the composition.</param>
    /// <param name="registrationContext">Context for the registration.</param>
    public void RegisterConventions(
        IConventionsBuilder builder,
        IEnumerable<TypeInfo> candidateTypes,
        ICompositionRegistrationContext registrationContext)
    {
        //... here you can use the conventions builder to register your services using the fluent API. The candidate types are provided if you need the  identified application types. A couple of examples are provided below:

        // shared/singleton service exported as IMyService with MyService implementation.
        builder.ForType(typeof(MyServiceImpl))
               .Export(b => b.AsContractType(typeof(IMyService)))
               .Shared();

        // instance-based multiple services exported as IMultiImplService
        builder.ForTypesDerivedFrom(typeof(IMultiImplService))
               .Export(b => b.AsContractType(typeof(IMultiImplService)));
    }

但是，还有第二种注册服务的方法，通过服务描述符而不是fluent API来注册服务。对于这种情况，请按照以下步骤操作：

• 定义一个实现IAppServiceInfoProvider的类。
• 返回所需服务的描述符。

与上述注册相同的示例代码：

public class MyAppServiceInfoProvider : IAppServiceInfoProvider
{
    /// <summary>
    /// Gets an enumeration of application service information objects.
    /// </summary>
    /// <param name="candidateTypes">The candidate types which can take part in the composition.</param>
    /// <param name="registrationContext">Context for the registration.</param>
    /// <returns>
    /// An enumeration of application service information objects and their associated contract type.
    /// </returns>
    public IEnumerable<(TypeInfo contractType, IAppServiceInfo appServiceInfo)> GetAppServiceInfos(IEnumerable<TypeInfo> candidateTypes, ICompositionRegistrationContext registrationContext)
    {
        yield return (typeof(IMyService).GetTypeInfo(), 
                      new AppServiceInfo(typeof(IMyService), 
                                         typeof(MyServiceImpl),
                                         AppServiceLifetime.Shared));
        yield return (typeof(IMultiImplService).GetTypeInfo(), 
                      new AppServiceInfo(typeof(IMultiImplService), 
                                         AppServiceLifetime.Instance, 
                                         allowMultiple: true));
    }

这两种情况都是自动发现的，并在适当的时候调用注册方法。但是，在第二种情况下，好处是注册可以作为稍后查询的服务元数据使用。