是不是我们日常的代码中也有这样的类型转换代码，不是说不好，只是类型转换也是有性能损失的，如果能换中方式可以同样实现而且还避免以上问题岂不是更好，这样我们的代码也更好维护和扩展，下面我们通过使用枚举类的方式来解决这个问题。
三、使用枚举类而不是枚举类型
public class Enumeration: IComparable { private readonly int _value; private readonly string _displayName; protected Enumeration() { } protected Enumeration(int value, string displayName) { _value = value; _displayName = displayName; } public int Value { get { return _value; } } public string DisplayName { get { return _displayName; } } public override string ToString() { return DisplayName; } public static IEnumerable<T> GetAll<T>() where T : Enumeration, new() { var type = typeof(T); var fields = type.GetFields(BindingFlags.Public | BindingFlags.Static | BindingFlags.DeclaredOnly); foreach (var info in fields) { var instance = new T(); var locatedValue = info.GetValue(instance) as T; if (locatedValue != null) { yield return locatedValue; } } } public override bool Equals(object obj) { var otherValue = obj as Enumeration; if (otherValue == null) { return false; } var typeMatches = GetType().Equals(obj.GetType()); var valueMatches = _value.Equals(otherValue.Value); return typeMatches && valueMatches; } public override int GetHashCode() { return _value.GetHashCode(); } public static int AbsoluteDifference(Enumeration firstValue, Enumeration secondValue) { var absoluteDifference = Math.Abs(firstValue.Value - secondValue.Value); return absoluteDifference; } public static T FromValue<T>(int value) where T : Enumeration, new() { var matchingItem = parse<T, int>(value, "value", item => item.Value == value); return matchingItem; } public static T FromDisplayName<T>(string displayName) where T : Enumeration, new() { var matchingItem = parse<T, string>(displayName, "display name", item => item.DisplayName == displayName); return matchingItem; } private static T parse<T, K>(K value, string description, Func<T, bool> predicate) where T : Enumeration, new() { var matchingItem = GetAll<T>().FirstOrDefault(predicate); if (matchingItem == null) { var message = string.Format("'{0}' is not a valid {1} in {2}", value, description, typeof(T)); throw new ApplicationException(message); } return matchingItem; } public int CompareTo(object other) { return Value.CompareTo(((Enumeration)other).Value); } }
public class Volume: Enumeration { private Volume() { throw new Exception(""); } private Volume(int value, string displayName): base(value, displayName) { } public static readonly Volume Low = new Volume(1, nameof(Low).ToLowerInvariant()); public static readonly Volume Medium = new Volume(2, nameof(Medium).ToLowerInvariant()); public static readonly Volume High = new Volume(3, nameof(High).ToLowerInvariant()); public static IEnumerable<Volume> List() => new[] { Low, Medium, High }; public static Volume From(int value) { var state = List().SingleOrDefault(s => s.Value == value); if (state == null) { throw new Exception($"Possible values for Volume: {String.Join(",", List().Select(s => s.Value))}"); } return state; } public static Volume FromName(string name) { var state = List() .SingleOrDefault(s => String.Equals(s.DisplayName, name, StringComparison.CurrentCultureIgnoreCase)); if (state == null) { throw new Exception($"Possible values for Volume: {String.Join(",", List().Select(s => s.DisplayName))}"); } return state; } }
static void Main(string[] args) { //EnumTricks.IsVolumeHigh((Volume)27); //var tmp = Enum.IsDefined(typeof(Volume), 3); //var str = EnumTricks.EnumToString((Volume)27); //var str2 = EnumTricks.EnumToString((Volume)3); //Console.WriteLine($"Volume 27:{str}"); //Console.WriteLine($"Volume 3:{str2}"); Console.WriteLine("------------------------------------------------------------"); Console.WriteLine(Volume.High.Value); Console.WriteLine(Volume.High.DisplayName); var volume = Volume.From(2); var volume2 = Volume.FromName("high"); var none = Volume.From(27); Console.ReadKey(); }
四、应用
代码如下：
Error文件下：
public interface ICommonError { int GetErrCode(); string GetErrMsg(); ICommonError SetErrMsg(string errMsg); }