C＃枚举数组接受错误值[重复]

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Why does casting int to invalid enum value NOT throw exception? 4 answers
为什么将int转换为无效的枚举值而不抛出异常？ 4个答案

I was working on a web service method that will receive an array of ints as parameter, and then, inside the method, I converted the values in the array into enum values, and stored them in a enum list. However, when a value that's not in the enum is passed, it is added to the enum list with no problems. No InvalidCastException, nothing. I made a test project that looks like this:

我正在研究一个Web服务方法，它将接收一个int数组作为参数，然后，在方法内部，我将数组中的值转换为枚举值，并将它们存储在枚举列表中。但是，当传递不在枚举中的值时，它将被添加到枚举列表中而没有任何问题。没有InvalidCastException，没有。我做了一个看起来像这样的测试项目：

static class Program
{
    static void Main(string[] args)
    {
        List<TestValues> values = new List<TestValues>() {
            TestValues.Value1,
            TestValues.Value2,
            (TestValues)15
        };

        foreach (var val in values)
            Console.WriteLine(val);

        Console.Read();
    }

    enum TestValues
    { 
        Value1 = 2,
        Value2 = 4,
        Value3 = 8
    }
}

When I run it, the output is:

当我运行它时，输出是：

Value1
Value2
15

For my web service, I'll implement a validation, so this will never hapen at all. But... this is weird! Shouldn't the runtime throw a InvalidCastException or ArgumentOutOfRangeException, or something similar? Since I got a list of enums (and not int values), I want the values to be limitted to the values of the enum (that's what an enum is for).

对于我的Web服务，我将实现验证，因此这根本不会有任何问题。但是......这很奇怪！不应该运行时抛出InvalidCastException或ArgumentOutOfRangeException，或类似的东西？由于我得到了一个枚举列表（而不是int值），我希望将值限制为枚举值（这就是枚举的用途）。

Am I missing something? Is this a .NET bug, a C# bug or is there something I don't know with enums?

我错过了什么吗？这是一个.NET错误，一个C＃错误还是存在一些我不知道的枚举？

5 个解决方案

#1

You can assign any value to an enum that the underlying type allows. By default, the underlying type is int, so you can assign any int value to the enum.

您可以将任何值分配给基础类型允许的枚举。默认情况下，基础类型为int，因此您可以将任何int值分配给枚举。

The main reason for this is because if you have a [Flags] enumeration, you want to be able to assign composite values:

这样做的主要原因是，如果您有[Flags]枚举，您希望能够分配复合值：

[Flags]
public enum MyFlags
{
    A = 1,
    B = 2
}

MyFlags flags = (MyFlags)3; // Equivalent to setting A and B

Preferably you'd just use the enumeration values to do that, though:

但是，您最好只使用枚举值来执行此操作：

MyFlags flags = MyFlags.A | MyFlags.B; // Sets flags to 3

It's important to note, of course, that the [Flags] attribute isn't required to enable this assignment. All enums have this property, by design.

当然，重要的是要注意，启用此分配不需要[Flags]属性。根据设计，所有的枚举都有这个属性。

As pointed out by a number of people, you can use Enum.IsDefined() to determine if a particular value is valid for a given enum. That should help with your validation.

正如许多人所指出的，您可以使用Enum.IsDefined（）来确定特定值是否对给定的枚举有效。这应该有助于您的验证。

#2

Yes, there is no check for defined values when you convert to an enum value.

是的，转换为枚举值时，不会检查定义的值。

You can use the IsDefined method to check if a specific value is defined:

您可以使用IsDefined方法检查是否定义了特定值：

if (Enum.IsDefined(typeof(TestValues), value)) ...

#3

You can always cast any int value to an enum based on int. This is by design, as the cast would be a lot slower if it had to check all legal values.

您始终可以基于int将任何int值转换为枚举。这是设计，因为如果必须检查所有合法值，演员会慢得多。

#4

You should read the following thread:

您应该阅读以下主题：

Why does Enum.Parse create undefined entries?

为什么Enum.Parse会创建未定义的条目？

In short, this is valid. If you want to check if the value is defined, use Enum.IsDefined.

简而言之，这是有效的。如果要检查是否已定义值，请使用Enum.IsDefined。

#5

To determine if the specified int is defined within the enum you can use Enum.IsDefined.

要确定是否在枚举中定义了指定的int，可以使用Enum.IsDefined。

Enum.IsDefined(typeof(TestValues), 15);

#1