c# - 用标志方法扩展枚举？

Question

我找到了有关如何创建扩展方法以从按位枚举中读出单个值的好示例。但现在 C# 4 已经添加了 HasFlag 方法，它们真的不需要了。

我认为真正有用的是对 SET a single flag 的扩展!
我有很多情况需要单独设置标志值。
我想要一个带有这个签名的扩展方法:

enumVariable.SetFlag(EnumType.SingleFlag, true);

或者可能:

enumVariable.SetFlag<EnumType>(EnumType.SingleFlag, true);

Answer 1

今天我在 http://hugoware.net/blog/enums-flags-and-csharp 上找到了解决方案.谢谢雨果!优秀的代码，工作正常。我稍微调整了它并将其添加到我现有的 EnumExtender 中:

public static class EnumExtender
{
    /// <summary>
    /// Adds a flag value to enum.
    /// Please note that enums are value types so you need to handle the RETURNED value from this method.
    /// Example: myEnumVariable = myEnumVariable.AddFlag(CustomEnumType.Value1);
    /// </summary>
    public static T AddFlag<T>(this Enum type, T enumFlag)
    {
        try
        {
            return (T)(object)((int)(object)type|(int)(object)enumFlag);
        }
        catch(Exception ex)
        {
            throw new ArgumentException(string.Format("Could not append flag value {0} to enum {1}",enumFlag, typeof(T).Name), ex);
        }
    }

    /// <summary>
    /// Removes the flag value from enum.
    /// Please note that enums are value types so you need to handle the RETURNED value from this method.
    /// Example: myEnumVariable = myEnumVariable.RemoveFlag(CustomEnumType.Value1);
    /// </summary>
    public static T RemoveFlag<T>(this Enum type, T enumFlag)
    {
        try
        {
            return (T)(object)((int)(object)type & ~(int)(object)enumFlag);
        }
        catch (Exception ex)
        {
            throw new ArgumentException(string.Format("Could not remove flag value {0} from enum {1}", enumFlag, typeof(T).Name), ex);
        }
    }

    /// <summary>
    /// Sets flag state on enum.
    /// Please note that enums are value types so you need to handle the RETURNED value from this method.
    /// Example: myEnumVariable = myEnumVariable.SetFlag(CustomEnumType.Value1, true);
    /// </summary>
    public static T SetFlag<T>(this Enum type, T enumFlag, bool value)
    {
        return value ? type.AddFlag(enumFlag) : type.RemoveFlag(enumFlag);
    }

    /// <summary>
    /// Checks if the flag value is identical to the provided enum.
    /// </summary>
    public static bool IsIdenticalFlag<T>(this Enum type, T enumFlag)
    {
        try
        {
            return (int)(object)type == (int)(object)enumFlag;
        }
        catch
        {
            return false;
        }
    }

    /// <summary>
    /// Convert provided enum type to list of values.
    /// This is convenient when you need to iterate enum values.
    /// </summary>
    public static List<T> ToList<T>()
    {
        if (!typeof(T).IsEnum)
            throw new ArgumentException();
        var values = Enum.GetNames(typeof(T));
        return values.Select(value => value.ToEnum<T>()).ToList();
    }

    /// <summary>
    /// Present the enum values as a comma separated string.
    /// </summary>
    public static string GetValues<T>()
    {
        if (!typeof(T).IsEnum)
            throw new ArgumentException();
        var values = Enum.GetNames(typeof(T));
        return string.Join(", ", values);
    }

}