编辑：添加了一些示例代码，探索了许多（也许是全部？）遍历数组的可能方式。
默认情况下，枚举类型被认为是从 int“派生”的。如果需要，您可以选择从其他整数类型之一派生它，例如字节、短、长等。
在这两种情况下，对 Enum.GetValues 的调用都会返回一个 ReportStatus 对象数组。
在第一个循环中使用 var 关键字告诉编译器使用数组的指定类型 ReportStatus 来确定 value 变量的类型。枚举的 ToString 实现是返回枚举条目的名称，而不是它表示的整数值，这就是名称从第一个循环输出的原因。
在第二个循环中使用 int 变量会导致 Enum.GetValues 返回的值从 ReportStatus 隐式转换为 int。当然，在 int 上调用 ToString 会返回一个表示整数值的字符串。隐式转换是导致行为差异的原因。
更新：正如其他人所指出的，Enum.GetValues 函数返回一个类型为 Array 的对象，因此它是 Object 类型的可枚举，而不是 ReportStatus 类型。
不管是遍历Array还是ReportStatus[]，最终结果都是一样的：
class Program
{
enum ReportStatus
{
Assigned = 1,
Analyzed = 2,
Written = 3,
Reviewed = 4,
Finished = 5,
}
static void Main(string[] args)
{
WriteValues(Enum.GetValues(typeof(ReportStatus)));
ReportStatus[] values = new ReportStatus[] {
ReportStatus.Assigned,
ReportStatus.Analyzed,
ReportStatus.Written,
ReportStatus.Reviewed,
ReportStatus.Finished,
};
WriteValues(values);
}
static void WriteValues(Array values)
{
foreach (var value in values)
{
Console.WriteLine(value);
}
foreach (int value in values)
{
Console.WriteLine(value);
}
}
static void WriteValues(ReportStatus[] values)
{
foreach (var value in values)
{
Console.WriteLine(value);
}
foreach (int value in values)
{
Console.WriteLine(value);
}
}
}
为了一些额外的乐趣，我在下面添加了一些代码，演示了使用 foreach 循环迭代指定数组的几种不同方法，包括详细描述每种情况下发生的情况的 cmets。
class Program
{
enum ReportStatus
{
Assigned = 1,
Analyzed = 2,
Written = 3,
Reviewed = 4,
Finished = 5,
}
static void Main(string[] args)
{
Array values = Enum.GetValues(typeof(ReportStatus));
Console.WriteLine("Type of array: {0}", values.GetType().FullName);
// Case 1: iterating over values as System.Array, loop variable is of type System.Object
// The foreach loop uses an IEnumerator obtained from System.Array.
// The IEnumerator's Current property uses the System.Array.GetValue method to retrieve the current value, which uses the TypedReference.InternalToObject function.
// The value variable is passed to Console.WriteLine(System.Object).
// Summary: 0 box operations, 0 unbox operations, 1 usage of TypedReference
Console.WriteLine("foreach (object value in values)");
foreach (object value in values)
{
Console.WriteLine(value);
}
// Case 2: iterating over values as System.Array, loop variable is of type ReportStatus
// The foreach loop uses an IEnumerator obtained from System.Array.
// The IEnumerator's Current property uses the System.Array.GetValue method to retrieve the current value, which uses the TypedReference.InternalToObject function.
// The current value is immediatly unboxed as ReportStatus to be assigned to the loop variable, value.
// The value variable is then boxed again so that it can be passed to Console.WriteLine(System.Object).
// Summary: 1 box operation, 1 unbox operation, 1 usage of TypedReference
Console.WriteLine("foreach (ReportStatus value in values)");
foreach (ReportStatus value in values)
{
Console.WriteLine(value);
}
// Case 3: iterating over values as System.Array, loop variable is of type System.Int32.
// The foreach loop uses an IEnumerator obtained from System.Array.
// The IEnumerator's Current property uses the System.Array.GetValue method to retrieve the current value, which uses the TypedReference.InternalToObject function.
// The current value is immediatly unboxed as System.Int32 to be assigned to the loop variable, value.
// The value variable is passed to Console.WriteLine(System.Int32).
// Summary: 0 box operations, 1 unbox operation, 1 usage of TypedReference
Console.WriteLine("foreach (int value in values)");
foreach (int value in values)
{
Console.WriteLine(value);
}
// Case 4: iterating over values as ReportStatus[], loop variable is of type System.Object.
// The foreach loop is compiled as a simple for loop; it does not use an enumerator.
// On each iteration, the current element of the array is assigned to the loop variable, value.
// At that time, the current ReportStatus value is boxed as System.Object.
// The value variable is passed to Console.WriteLine(System.Object).
// Summary: 1 box operation, 0 unbox operations
Console.WriteLine("foreach (object value in (ReportStatus[])values)");
foreach (object value in (ReportStatus[])values)
{
Console.WriteLine(value);
}
// Case 5: iterating over values as ReportStatus[], loop variable is of type ReportStatus.
// The foreach loop is compiled as a simple for loop; it does not use an enumerator.
// On each iteration, the current element of the array is assigned to the loop variable, value.
// The value variable is then boxed so that it can be passed to Console.WriteLine(System.Object).
// Summary: 1 box operation, 0 unbox operations
Console.WriteLine("foreach (ReportStatus value in (ReportStatus[])values)");
foreach (ReportStatus value in (ReportStatus[])values)
{
Console.WriteLine(value);
}
// Case 6: iterating over values as ReportStatus[], loop variable is of type System.Int32.
// The foreach loop is compiled as a simple for loop; it does not use an enumerator.
// On each iteration, the current element of the array is assigned to the loop variable, value.
// The value variable is passed to Console.WriteLine(System.Int32).
// Summary: 0 box operations, 0 unbox operations
Console.WriteLine("foreach (int value in (ReportStatus[])values)");
foreach (int value in (ReportStatus[])values)
{
Console.WriteLine(value);
}
// Case 7: The compiler evaluates var to System.Object. This is equivalent to case #1.
Console.WriteLine("foreach (var value in values)");
foreach (var value in values)
{
Console.WriteLine(value);
}
// Case 8: The compiler evaluates var to ReportStatus. This is equivalent to case #5.
Console.WriteLine("foreach (var value in (ReportStatus[])values)");
foreach (var value in (ReportStatus[])values)
{
Console.WriteLine(value);
}
}
}
-- 在上面的示例中更新了我的 cmets；经过仔细检查，我发现 System.Array.GetValue 方法实际上使用 TypedReference 类来提取数组的元素并将其作为 System.Object 返回。我最初写过那里发生了拳击操作，但从技术上讲并非如此。我不确定框操作与对 TypedReference.InternalToObject 的调用的比较是什么；我认为这取决于 CLR 实现。无论如何，我相信现在的细节或多或少是正确的。