将数组转换为 IEnumerable

假设你有基本的Employee类如下：

class Employee
{
   public string Name;
   public int Years;
   public string Department;
}

然后（在一个单独的类中）我有以下代码片段（我想我理解除了最后一个之外的所有代码片段）：

我相信以下代码片段有效，因为数组初始化程序创建了一个 Employee 对象数组，这些对象与分配给的劳动力变量的类型相同。

Employee[] workforceOne = new Employee[] {
   new Employee() { Name = "David", Years = 0, Department = "software" },
   new Employee() { Name = "Dexter", Years = 3, Department = "software" },
   new Employee() { Name = "Paul", Years = 4, Department = "software" } };

然后我有以下代码片段。我相信这是有效的，因为数组Employee对象隐式是 Array() 类的实现，该类实现IEnumerable。因此，我相信这就是为什么数组可以分配给IEnumerable的原因？

IEnumerable workforceTwo = new Employee[] {
   new Employee() { Name = "David", Years = 0, Department = "software" },
   new Employee() { Name = "Dexter", Years = 3, Department = "software" },
   new Employee() { Name = "Paul", Years = 4, Department = "software" } };

然后我有这个代码片段：

IEnumerable<Employee> workforceThree = new Employee[] {
   new Employee() { Name = "David", Years = 0, Department = "software" },
   new Employee() { Name = "Dexter", Years = 3, Department = "software" },
   new Employee() { Name = "Paul", Years = 4, Department = "software" } };

我不确定这个代码片段为什么有效？ IEnumerable<Employee>继承自IEnumerable（并覆盖（或重载？）GetEnumerator()方法），但我不应该因此需要对上述内容进行强制转换才能这样工作：

//The cast does work but is not required
IEnumerable<Employee> workforceFour = (IEnumerable<Employee>)new Employee[] {
   new Employee() { Name = "David", Years = 0, Department = "software" },
   new Employee() { Name = "Dexter", Years = 3, Department = "software" },
   new Employee() { Name = "Paul", Years = 4, Department = "software" } };

看起来该数组是从一种类型隐式向下转换的IEnumerable to IEnumerable<Employee>但我一直认为，当您需要将类型转换为更具体的类型时，您需要显式强制转换。

也许我在这里缺少一些简单的理解，但有人可以帮助我理解这一点。

谢谢。

From 文档 http://msdn.microsoft.com/en-us/library/system.array.aspx:

在 .NET Framework 2.0 版中，Array 类实现System.Collections.Generic.IList<T>, System.Collections.Generic.ICollection<T>, and System.Collections.Generic.IEnumerable<T>通用接口。这些实现在运行时提供给数组，因此对文档构建工具不可见。因此，泛型接口不会出现在 Array 类的声明语法中，并且不存在只能通过将数组强制转换为泛型接口类型（显式接口实现）才能访问的接口成员的参考主题。

因此，你的Employee[]实施IEnumerable<Employee>.