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背景：按位枚举对于“更具可读性”的比较和检查很有用：即OpenFile(write | append).

我已经看到了几种在 C# 中声明按位枚举的方法，但最近其中一种常见模式似乎不再返回唯一值，我想知道我是在声明它错误还是某些地方发生了变化。我说的是“DWORD”（十六进制？）样式（如下所示），在 VS2012 RC 中枚举时给出的值是 1、2、3、4 ......而不是预期的按位加倍。

其他人可以重现这个吗？我将用于验证的代码与控制台输出一起发布；ComparisonsDword正如您从“标志枚举，带 DWORD 的显式值”的输出中看到的那样，发生了奇怪的行为。

没有标志，正常枚举

/// <summary>
/// How to compare filter values; no underlying type declared, not flag
/// </summary>
public enum ComparisonsNotInt {
    [Description("x")]
    None
    ,
    [Description("!=")]
    NotEqual
    ,
    [Description("=")]
    Equal
    ,
    [Description(">")]
    GreaterThan
    ,
    [Description("<")]
    LessThan
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsNotFlag

没有标志，基础类型 = int

/// <summary>
/// How to compare filter values, not flag but underlying type declared
/// </summary>
public enum ComparisonsNotFlag : int {
    [Description("x")]
    None
    ,
    [Description("!=")]
    NotEqual
    ,
    [Description("=")]
    Equal
    ,
    [Description(">")]
    GreaterThan
    ,
    [Description("<")]
    LessThan
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsNotFlag

标志，隐含值

/// <summary>
/// How to compare filter values; values default to whatever .NET decides
/// </summary>
[Flags]
public enum ComparisonsImplicit : int {
    [Description("x")]
    None
    ,
    [Description("!=")]
    NotEqual
    ,
    [Description("=")]
    Equal
    ,
    [Description(">")]
    GreaterThan
    ,
    [Description("<")]
    LessThan
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsImplicit

标志，显式值

/// <summary>
/// How to compare filter values; values explicitly defined with doubled numbers
/// </summary>
[Flags]
public enum ComparisonsExplicit : int {
    [Description("x")]
    None = 0
    ,
    [Description("!=")]
    NotEqual = 1
    ,
    [Description("=")]
    Equal = 2
    ,
    [Description(">")]
    GreaterThan = 4
    ,
    [Description("<")]
    LessThan = 8
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsExplicit

标志，使用 DWORD 样式的显式值 注意：这是没有正确提供唯一值的原因，因此像这样的组合GreaterThanOrEqual会失败。

/// <summary>
/// How to compare filter values; values explicitly defined with DWORD style
/// </summary>
[Flags]
public enum ComparisonsDword : int {
    [Description("x")]
    None = 0x0
    ,
    [Description("!=")]
    NotEqual = 0x1
    ,
    [Description("=")]
    Equal = 0x2
    ,
    [Description(">")]
    GreaterThan = 0x3
    ,
    [Description("<")]
    LessThan = 0x4
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsDword

标志，使用 DWORD 样式的显式值 注意：也是不适当的值，只是检查底层类型是否影响问题。

/// <summary>
/// How to compare filter values; values explicitly defined with DWORD style
/// </summary>
[Flags]
public enum ComparisonsDwordNotInt {
    [Description("x")]
    None = 0x0
    ,
    [Description("!=")]
    NotEqual = 0x1
    ,
    [Description("=")]
    Equal = 0x2
    ,
    [Description(">")]
    GreaterThan = 0x3
    ,
    [Description("<")]
    LessThan = 0x4
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsDword

标志，使用位移样式的显式值

/// <summary>
/// How to compare filter values; values explicitly set using shorthand of bitwise shifting
/// </summary>
[Flags]
public enum ComparisonsBitshift : int {
    [Description("x")]
    None = 0
    ,
    [Description("!=")]
    NotEqual = 1 << 0
    ,
    [Description("=")]
    Equal = 1 << 1
    ,
    [Description(">")]
    GreaterThan = 1 << 2
    ,
    [Description("<")]
    LessThan = 1 << 3
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
    /// </summary>
    [Description("<=")]
    LessThanOrEqual = (Equal | LessThan)
    ,
    /// <summary>
    /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
    /// </summary>
    [Description(">=")]
    GreaterThanOrEqual = (Equal | GreaterThan)
}//--   enum    ComparisonsBitshift

枚举输出：

    Plain enum ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThan      ,        Descr = >,     Value = 3
    Enum = GreaterThan      ,        Descr = >,     Value = 3   // bad: should be GTE
    Enum = LessThan         ,        Descr = <,     Value = 4
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 6

    Plain enum, underlying int ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThan      ,        Descr = >,     Value = 3
    Enum = GreaterThan      ,        Descr = >,     Value = 3   // bad: should be GTE
    Enum = LessThan         ,        Descr = <,     Value = 4
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 6

    Flag enum, implicit values ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 3   // bad: should be GT
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 3
    Enum = LessThan         ,        Descr = <,     Value = 4
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 6

    Flag enum, explicit values ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThan      ,        Descr = >,     Value = 4
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 6
    Enum = LessThan         ,        Descr = <,     Value = 8
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 10

    Flag enum, explicit values with DWORD ----                  // all of these are weirdly unexpected
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 3
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 3
    Enum = LessThan         ,        Descr = <,     Value = 4
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 6

    Flag enum, explicit values with DWORD, not underlying int ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 3
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 3
    Enum = LessThan         ,        Descr = <,     Value = 4
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 6

    Flag enum, explicit values with bitshifting ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThan      ,        Descr = >,     Value = 4
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 6
    Enum = LessThan         ,        Descr = <,     Value = 8
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 10

参考：

  1. C# 中的 [Flags] 枚举属性是什么意思？
  2. MSDN 枚举类型
  3. MSDN 标志属性
  4. 不期望按位枚举转换返回值

为了完整起见，我正在用@kirk-woll 的答案中的正确用法修改我原来的问题

更正了 DWORD 语法

    /// <summary>
    /// How to compare filter values; values explicitly defined with *correct* DWORD style
    /// </summary>
    [Flags]
    public enum ComparisonsDwordCorrectlyDefined {
        [Description("x")]
        None = 0x0
        ,
        [Description("!=")]
        NotEqual = 0x1
        ,
        [Description("=")]
        Equal = 0x2
        ,
        [Description(">")]
        GreaterThan = 0x4
        ,
        [Description("<")]
        LessThan = 0x8
        ,
        /// <summary>
        /// Combination of <see cref="Equal"/> and <see cref="LessThan"/>
        /// </summary>
        [Description("<=")]
        LessThanOrEqual = (Equal | LessThan)
        ,
        /// <summary>
        /// Combination of <see cref="Equal"/> and <see cref="GreaterThan"/>
        /// </summary>
        [Description(">=")]
        GreaterThanOrEqual = (Equal | GreaterThan)
    }//--   enum    ComparisonsDwordCorrectlyDefined

枚举输出

    Flag enum, explicit values with correct DWORD ----
    Enum = None             ,        Descr = x,     Value = 0
    Enum = NotEqual         ,        Descr = !=,    Value = 1
    Enum = Equal            ,        Descr = =,     Value = 2
    Enum = GreaterThan      ,        Descr = >,     Value = 4
    Enum = GreaterThanOrEqual,       Descr = >=,    Value = 6
    Enum = LessThan         ,        Descr = <,     Value = 8
    Enum = LessThanOrEqual  ,        Descr = <=,    Value = 10
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1 回答 1

5

你的 DWORD 十六进制样式是错误的。你是加一而不是加倍：

NotEqual = 0x1
Equal = 0x2
GreaterThan = 0x3
LessThan = 0x4

应该：

NotEqual = 0x1
Equal = 0x2
GreaterThan = 0x4
LessThan = 0x8

当然，在您开始使用 hex 样式之前，它显然没有用处8：

LessThan = 0x8
GreaterThanOrEqual = 0x10
LessThanOrEqual = 0x20

在这里它有点方便，因为加倍的进程会导致一个简化的模式，而不是必须在你的脑海中把它加倍。

于 2012-06-21T16:23:13.840 回答