/// <summary>
/// 尝试获取指定类型的服务描述符。
/// </summary>
/// <param name="services">给定的 <see cref="IServiceCollection"/>。</param>
/// <param name="serviceType">给定的服务类型。</param>
/// <param name="predicate">给定的断定工厂方法。</param>
/// <param name="descriptor">输出 <see cref="ServiceDescriptor"/>。</param>
/// <returns>返回是否成功获取的布尔值。</returns>
public static bool TryGetSingle(this IServiceCollection services, Type serviceType,
Func <ServiceDescriptor, bool> predicate, out ServiceDescriptor descriptor)
{
services.NotNull(nameof(services));
// 存在多个相同服务与实现类型的服务集合
descriptor = services.Where(GetPredicateDescriptor(serviceType))
.SingleOrDefault(predicate);
return(descriptor.IsNotNull());
}
