[Asp.net 5] DependencyInjection项目代码分析4-微软的实现（5）（IEnumerable<>补充）

Asp.net 5的依赖注入注入系列可以参考链接： [Asp.net 5] DependencyInjection项目代码分析-目录

我们在之前讲微软的实现时，对于OpenIEnumerableService与ClosedIEnumerableService抛下没讲，现在我们就将该部分补充完整。

我们回忆ServiceProvider类的构造函数（对外部使用的）中，注册了IEnumerable<>、new OpenIEnumerableService(_table)的关系。

internal class ClosedIEnumerableService : IService
{
private readonly Type _itemType;
private readonly ServiceEntry _serviceEntry;

public ClosedIEnumerableService(Type itemType, ServiceEntry entry)
{
_itemType = itemType;
_serviceEntry = entry;
}

public IService Next { get; set; }

public ServiceLifetime Lifetime
{
get { return ServiceLifetime.Transient; }
}

public IServiceCallSite CreateCallSite(ServiceProvider provider, ISet<Type> callSiteChain)
{
var list = new List<IServiceCallSite>();
for (var service = _serviceEntry.First; service != null; service = service.Next)
{
list.Add(provider.GetResolveCallSite(service, callSiteChain));
}
return new CallSite(_itemType, list.ToArray());
}

private class CallSite : IServiceCallSite
{
private readonly Type _itemType;
private readonly IServiceCallSite[] _serviceCallSites;

public CallSite(Type itemType, IServiceCallSite[] serviceCallSites)
{
_itemType = itemType;
_serviceCallSites = serviceCallSites;
}

public object Invoke(ServiceProvider provider)
{
var array = Array.CreateInstance(_itemType, _serviceCallSites.Length);
for (var index = 0; index != _serviceCallSites.Length; ++index)
{
array.SetValue(_serviceCallSites[index].Invoke(provider), index);
}
return array;
}

public Expression Build(Expression provider)
{
return Expression.NewArrayInit(
_itemType,
_serviceCallSites.Select(callSite =>
Expression.Convert(
callSite.Build(provider),
_itemType)));
}
}
}

ClosedIEnumerableService
[之前我们介绍ServiceEntry时，明确指出是链表结构，而不是单独存放一个值；其应用在这进行了淋漓尽致的表现]