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背景：ビット単位の列挙型は、「より読みやすい」比較とチェックに役立ちOpenFile(write | append)ます。

C＃でビット単位の列挙型を宣言する方法をいくつか見てきましたが、最近、一般的なパターンの1つが一意の値を返さなくなったようで、間違って宣言しているのか、何かが変更されているのか疑問に思いました。「DWORD」（hex？）スタイル（以下に示す）について話しています。これは、VS2012 RCで列挙すると、予想されるビット単位の倍増ではなく、1、2、3、4...として値を返します。

他の誰かがこれを再現できますか？検証に使用したコードをコンソール出力と一緒に投稿しています。ComparisonsDword「フラグ列挙型、DWORDを使用した明示的な値」の出力からわかるように、奇妙な動作が発生します。

フラグなし、通常の列挙型

/// <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

フラグなし、基になるタイプ= 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

フラグ、暗黙の値

/// <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

フラグ、明示的な値

/// <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

フラグ、DWORDスタイルを使用した明示的な値注 ：これは一意の値を正しく提供していないため、のような組み合わせはGreaterThanOrEqual失敗します。

/// <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

フラグ、DWORDスタイルを使用した明示的な値注 ：これも不適切な値であり、基になるタイプが問題に影響を与えているかどうかを確認するだけです。

/// <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

フラグ、ビットシフトスタイルを使用した明示的な値

/// <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

列挙からの出力：

    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

参照：

  1. [Flags] Enum AttributeはC＃で何を意味しますか？
  2. MSDN列挙型
  3. MSDN FlagsAttribute
  4. ビット単位の列挙型キャストの戻り値は予期されていません

完全を期すために、@kirk-wollの回答から正しい使用法で元の質問を修正しています

DWORD構文を修正しました

    /// <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

列挙からの出力

    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 に答える 1

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DWORDの16進スタイルが間違っています。倍増するのではなく、1ずつ増加します。

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

する必要があります：

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

もちろん、16進スタイルを使用することは、上に到達し始めるまで明らかに役に立ちません8。

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

ここでは、進行を2倍にすると、頭の中で精神的に2倍にする必要がなく、パターンが単純化されるため、便利です。

于 2012-06-21T16:23:13.840 に答える