如何在Unity中自动注册一个通用接口到该接口的非通用实现

Question

我的应用程序中有一个模式。

public interface ICommandService<TCommand>
{
public void Execute(TCommand command);
}

该接口由许多不同的服务类实现。下面是一个例子:

public class UpdateWidgetService : ICommandService<UpdateWidget>
{
public void Execute(UpdateWidget command)
{
...
}
}
public class UpdateWidget
{
...data
}

这些服务类在控制器和其他类中被依赖:

public class WidgetController
{
private readonly ICommandService<UpdateWidget> service;

public WidgetController(ICommandService<UpdateWidget> service)
{
this.service = service;
}

public ActionResult UpdateWidget(UpdateWidgetViewModel viewModel)
{
...
UpdateWidget command = viewModel.Command;
this.service.Execute(command);
}
}

如果我要手动注册所有类型映射，我认为像这样的东西会起作用:

container.RegisterType(typeof(ICommandService<UpdateWidget>), typeof(UpdateWidgetService));
container.RegisterType(typeof(ICommandService<CreateWidget>), typeof(CreateWidgetService));
container.RegisterType(typeof(ICommandService<DeleteGizmo>), typeof(DeleteGizmoService));
container.RegisterType(typeof(ICommandService<LaunchNuclearStrike>), typeof(LaunchNuclearStrikeService));

但是正如你所看到的，有一个约定，所有实现ICommandService<TCommand>的类都被命名为[TCommand]Service，我真的很想按照约定设置某种自动注册。到目前为止，我试过的都没有成功。我的问题似乎主要与泛型类型的论点。以下是目前为止的内容:

var container = new UnityContainer();
var assembly = Assembly.GetExecutingAssembly();
var commandServices = assembly.GetTypes().Where(type => !type.IsAbstract && type.Name.EndsWith("Service") && type.GetInterfaces().Single().Name.StartsWith("ICommandService")).ToList();
foreach (var service in commandServices)
{
var serviceInterface = service.GetInterfaces().Single();
var genericTypeArgument = serviceInterface.GenericTypeArguments.Single();
container.RegisterType(typeof(ICommandService<genericTypeArgument>), service);
}

我得到以下错误:"'genericTypeArgument'是一个变量，但被用作类型"

Answer 1

这是我在各种项目中用来解决这个问题的解决方案，最常见的是围绕领域驱动的事件处理程序(如IHandlerOf<DomainEvent>)或插件系统。

首先，指定要包含哪些程序集来进行类型发现。

var assemblies = RegistrationByConvention.FromSpecificAssemblies(
typeof(ClassInAssembly1).Assembly,
typeof(ClassInAssembly2).Assembly,
typeof(ClassInAssembly3).Assembly);

然后收集所有非抽象类型，非值类型，并且是可见的。

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
public class RegistrationByConvention
{
public static IEnumerable<Type> FromSpecificAssemblies(params Assembly[] assemblies)
{
return GetTypes(assemblies);
}
private static IEnumerable<Type> GetTypes(IEnumerable<Assembly> assemblies)
{
return assemblies.SelectMany(assembly =>
{
try
{
return GetTypes(assembly.DefinedTypes);
}
catch (ReflectionTypeLoadException ex)
{
return GetTypes(ex.Types.TakeWhile(x => x != null).Select(x => x.GetTypeInfo()));
}
});
}
private static IEnumerable<Type> GetTypes(IEnumerable<TypeInfo> typeInfos)
{
return typeInfos
.Where(x => x.IsClass & !x.IsAbstract && !x.IsValueType && x.IsVisible)
.Select(ti => ti.AsType());
}
}

最后，对于像您这样的通用实现，我使用IsAssignableFrom和MakeGenericType。我建议为UpdateWidget和其他小部件分配一个基类或接口，以使它们可被发现。

foreach (var matchingType in assemblies.Where((type) => { return typeof(BaseWidget).IsAssignableFrom(type); }))
{
container.RegisterTypes(
assemblies.Where((type) =>
{
return typeof(ICommandService<>).MakeGenericType(matchingType).IsAssignableFrom(type);
}),
WithMappings.FromAllInterfaces,
WithName.TypeName,
WithLifetime.Transient);
}

如果你只是想解决你的错误并使用你现有的代码，你会想在typeof(ICommandService<>).MakeGenericType(matchingType)中使用Type.MakeGenericType。

Answer 2

试试这个:

var container = new UnityContainer();
var assembly = Assembly.GetExecutingAssembly();
var commandServices = assembly.GetTypes().Where(type => !type.IsAbstract && type.Name.EndsWith("Service") && type.GetInterfaces().Single().Name.StartsWith("ICommandService")).ToList();
foreach (var service in commandServices)
{
var serviceInterface = service.GetInterfaces().Single();
var genericTypeArgument = serviceInterface.GenericTypeArguments.Single();
Type type = Type.GetType($"{genericTypeArgument.UnderlyingSystemType.ToString()}, {genericTypeArgument.Namespace}");
container.RegisterType(typeof(ICommandService<>), type, new TransientLifetimeManager());

}

Answer 3

看起来你的commandServices是类型，所以

foreach (var service in commandServices
{
foreach (var interfaceType in service.GetInterfaces())
{
container.RegisterType(interfaceType, service);
}
}