DescriptionAttribute特性可以用到很多地方,比較常見(jiàn)的就是枚舉,通過(guò)獲取枚舉上定義的描述信息在UI上顯示,一個(gè)簡(jiǎn)單的枚舉定義:
public enum EnumGender { None, [System.ComponentModel.Description("男")] Male, [System.ComponentModel.Description("女")] Female, Other, }
本文不討論DescriptionAttribute的其他應(yīng)用場(chǎng)景,也不關(guān)注多語(yǔ)言的實(shí)現(xiàn),只單純的研究下獲取枚舉描述信息的方法。
一般比較常見(jiàn)的獲取枚舉描述信息的方法如下,可以在園子里搜索類似的代碼非常多。
public static string GetDescriptionOriginal(this Enum @this) { var name = @this.ToString(); var field = @this.GetType().GetField(name); if (field == null) return name; var att = System.Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute), false); return att == null ? field.Name : ((DescriptionAttribute)att).Description; }
簡(jiǎn)單測(cè)試下:
Console.WriteLine(EnumGender.Female.GetDescriptionOriginal());Console.WriteLine(EnumGender.Male.GetDescriptionOriginal());Console.WriteLine(EnumGender.Other.GetDescriptionOriginal());
//輸出結(jié)果:
女
男
Other
首先要理解特性是什么?
特性:
Attribute特性就是關(guān)聯(lián)了一個(gè)目標(biāo)對(duì)象的一段配置信息,存儲(chǔ)在dll內(nèi)的元數(shù)據(jù)。它本身沒(méi)什么意義,可以通過(guò)反射來(lái)獲取配置的特性信息。
因此主要問(wèn)題其實(shí)就是反射造成的嚴(yán)重性能問(wèn)題:
性能到底有多差呢?代碼來(lái)實(shí)測(cè)一下:
[Test] public void GetDescriptionOriginal_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionOriginal(); } }); }); }//輸出結(jié)果:80TimeSpan:79,881.0000ms //共消耗了將近80秒MemoryUsed:-1,652.7970KBCollectionCount(0):7,990.00 //0代GC回收了7千多次,因?yàn)閯?chuàng)建了大量的DescriptionAttribute對(duì)象
其中this.GetTestEnums();方法使用獲取一個(gè)枚舉值集合,用于測(cè)試的,集合大小80,執(zhí)行100w次,相當(dāng)于執(zhí)行了8000w次GetDescriptionOriginal方法。
TestHelper.InvokeAndWriteAll方法是用來(lái)計(jì)算執(zhí)行前后的時(shí)間、內(nèi)存消耗、0代GC回收次數(shù)的,文末附錄中給出了代碼,由于內(nèi)存回收的原因,內(nèi)存消耗計(jì)算其實(shí)不準(zhǔn)確的,不過(guò)可以參考第三個(gè)指標(biāo)0代GC回收次數(shù)。
知道了問(wèn)題原因,解決就好辦了,基本思路就是把獲取到的文本值緩存起來(lái),一個(gè)枚舉值只反射一次,這樣性能問(wèn)題就解決了。
因?yàn)槭褂渺o態(tài)變量字典來(lái)緩存值,就涉及到線程安全,需要使用鎖(做了雙重檢測(cè)),具體方法:
PRivate static Dictionary<Enum, string> _LockDictionary = new Dictionary<Enum, string>(); public static string GetDescriptionByDictionaryWithLocak(this Enum @this) { if (_LockDictionary.ContainsKey(@this)) return _LockDictionary[@this]; Monitor.Enter(_obj); if (!_LockDictionary.ContainsKey(@this)) { var value = @this.GetDescriptionOriginal(); _LockDictionary.Add(@this, value); } Monitor.Exit(_obj); return _LockDictionary[@this]; }
來(lái)測(cè)試一下,測(cè)試數(shù)據(jù)、次數(shù)和1.2的GetDescriptionOriginal_Test相同,效率有很大的提升,只有一次內(nèi)存回收。
[Test] public void GetDescriptionByDictionaryWithLocak_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionByDictionaryWithLocak(); } }); }); }//測(cè)試結(jié)果:80TimeSpan:1,860.0000msMemoryUsed:159.2422KBCollectionCount(0):1.00
還是先看看實(shí)現(xiàn)方法吧!
private static Dictionary<Enum, string> _ExceptionDictionary = new Dictionary<Enum, string>(); public static string GetDescriptionByDictionaryWithException(this Enum @this) { try { return _ExceptionDictionary[@this]; } catch (KeyNotFoundException) { Monitor.Enter(_obj); if (!_ExceptionDictionary.ContainsKey(@this)) { var value = @this.GetDescriptionOriginal(); _ExceptionDictionary.Add(@this, value); } Monitor.Exit(_obj); return _ExceptionDictionary[@this]; } }
假設(shè)我們的使用場(chǎng)景是這樣的:項(xiàng)目定義的枚舉并不多,但是用其描述值很頻繁,比如定義了一個(gè)用戶性別枚舉,用的地方很多,使用頻率很高。
上面GetDescriptionByDictionaryWithLocak的方法中,第一句代碼“if (_LockDictionary.ContainsKey(@this)) ”就是驗(yàn)證是否包含枚舉值。在2.1的測(cè)試中執(zhí)行了8000w次,其中只有80次(總共只有80個(gè)枚舉值用于測(cè)試)需要這句代碼“if (_LockDictionary.ContainsKey(@this)) ”,其余的直接取值就可了。基于這樣的考慮,就有了上面的方法GetDescriptionByDictionaryWithException。
來(lái)測(cè)試一下,看看效果吧!
[Test] public void GetDescriptionByDictionaryWithException_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionByDictionaryWithException(); } }); }); }//測(cè)試結(jié)果:80TimeSpan:1,208.0000msMemoryUsed:230.9453KBCollectionCount(0):1.00
測(cè)試結(jié)果來(lái)看,基本上差不多,在時(shí)間上略微快樂(lè)一點(diǎn)點(diǎn),1,208.0000ms:1,860.0000ms,執(zhí)行8000w次快600毫秒,好像差別也不大啊,這是為什么呢?
這個(gè)其實(shí)就是Dictionary的問(wèn)題了,Dictionary內(nèi)部使用散列算法計(jì)算存儲(chǔ)地址,其查找的時(shí)間復(fù)雜度為o(1),他的查找效果是非常快的,而本方法中利用了異常處理,異常捕獲本身是有一定性能影響的。
ConcurrentDictionary是一個(gè)線程安全的字典類,代碼:
private static ConcurrentDictionary<Enum, string> _ConcurrentDictionary = new ConcurrentDictionary<Enum, string>(); public static string GetDescriptionByConcurrentDictionary(this Enum @this) { return _ConcurrentDictionary.GetOrAdd(@this, (key) => { var type = key.GetType(); var field = type.GetField(key.ToString()); return field == null ? key.ToString() : GetDescription(field); }); }
測(cè)試代碼及測(cè)試結(jié)果:
[Test] public void GetDescriptionByConcurrentDictionary_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionByConcurrentDictionary(); } }); }); }//測(cè)試結(jié)果:80TimeSpan:1,303.0000msMemoryUsed:198.0859KBCollectionCount(0):1.00
綜上所述,解決了性能問(wèn)題、位域枚舉問(wèn)題的正式的代碼:
/// <summary> /// 獲取枚舉的描述信息(Descripion)。 /// 支持位域,如果是位域組合值,多個(gè)按分隔符組合。 /// </summary> public static string GetDescription(this Enum @this) { return _ConcurrentDictionary.GetOrAdd(@this, (key) => { var type = key.GetType(); var field = type.GetField(key.ToString()); //如果field為null則應(yīng)該是組合位域值, return field == null ? key.GetDescriptions() : GetDescription(field); }); } /// <summary> /// 獲取位域枚舉的描述,多個(gè)按分隔符組合 /// </summary> public static string GetDescriptions(this Enum @this, string separator = ",") { var names = @this.ToString().Split(','); string[] res = new string[names.Length]; var type = @this.GetType(); for (int i = 0; i < names.Length; i++) { var field = type.GetField(names[i].Trim()); if (field == null) continue; res[i] = GetDescription(field); } return string.Join(separator, res); } private static string GetDescription(FieldInfo field) { var att = System.Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute), false); return att == null ? field.Name : ((DescriptionAttribute)att).Description; }
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1.EnumExtension.cs代碼:
public static class EnumExtension { /// <summary> /// 獲取枚舉的描述信息(Descripion)。 /// 支持位域,如果是位域組合值,多個(gè)按分隔符組合。 /// </summary> public static string GetDescription(this Enum @this) { return _ConcurrentDictionary.GetOrAdd(@this, (key) => { var type = key.GetType(); var field = type.GetField(key.ToString()); //如果field為null則應(yīng)該是組合位域值, return field == null ? key.GetDescriptions() : GetDescription(field); }); } /// <summary> /// 獲取位域枚舉的描述,多個(gè)按分隔符組合 /// </summary> public static string GetDescriptions(this Enum @this, string separator = ",") { var names = @this.ToString().Split(','); string[] res = new string[names.Length]; var type = @this.GetType(); for (int i = 0; i < names.Length; i++) { var field = type.GetField(names[i].Trim()); if (field == null) continue; res[i] = GetDescription(field); } return string.Join(separator, res); } private static string GetDescription(FieldInfo field) { var att = System.Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute), false); return att == null ? field.Name : ((DescriptionAttribute)att).Description; } /****************** test methods ******************/ public static string GetDescriptionOriginal(this Enum @this) { var name = @this.ToString(); var field = @this.GetType().GetField(name); if (field == null) return name; var att = System.Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute), false); return att == null ? field.Name : ((DescriptionAttribute)att).Description; } private static Dictionary<Enum, string> _LockDictionary = new Dictionary<Enum, string>(); public static string GetDescriptionByDictionaryWithLocak(this Enum @this) { if (_LockDictionary.ContainsKey(@this)) return _LockDictionary[@this]; Monitor.Enter(_obj); if (!_LockDictionary.ContainsKey(@this)) { var value = @this.GetDescriptionOriginal(); _LockDictionary.Add(@this, value); } Monitor.Exit(_obj); return _LockDictionary[@this]; } private static Dictionary<Enum, string> _ExceptionDictionary = new Dictionary<Enum, string>(); public static string GetDescriptionByDictionaryWithException(this Enum @this) { try { return _ExceptionDictionary[@this]; } catch (KeyNotFoundException) { Monitor.Enter(_obj); if (!_ExceptionDictionary.ContainsKey(@this)) { var value = @this.GetDescriptionOriginal(); _ExceptionDictionary.Add(@this, value); } Monitor.Exit(_obj); return _ExceptionDictionary[@this]; } } public static object _obj = new object(); private static ConcurrentDictionary<Enum, string> _ConcurrentDictionary = new ConcurrentDictionary<Enum, string>(); public static string GetDescriptionByConcurrentDictionary(this Enum @this) { return _ConcurrentDictionary.GetOrAdd(@this, (key) => { var type = key.GetType(); var field = type.GetField(key.ToString()); return field == null ? key.ToString() : GetDescription(field); }); } }
2.測(cè)試類EnumTest.cs代碼:
[TestFixture] public class EnumTest { [Test] public void SimpleTest() { Console.WriteLine(EnumGender.Female.GetDescriptionOriginal()); Console.WriteLine(EnumGender.Male.GetDescriptionOriginal()); Console.WriteLine(EnumGender.Other.GetDescriptionOriginal()); var t1 = EnumGender.Male | EnumGender.Female; Console.WriteLine((t1 & EnumGender.Male) == EnumGender.Male); Console.WriteLine(t1 & ~EnumGender.Male); Console.WriteLine(Enum.IsDefined(typeof(EnumGender), 0)); } [Test] public void GetDescriptionOriginal_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionOriginal(); } }); }); } [Test] public void GetDescriptionByDictionaryWithLocak_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionByDictionaryWithLocak(); } }); }); } [Test] public void GetDescriptionByDictionaryWithException_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionByDictionaryWithException(); } }); }); } [Test] public void GetDescriptionByConcurrentDictionary_Test() { var enums = this.GetTestEnums(); Console.WriteLine(enums.Count); TestHelper.InvokeAndWriteAll(() => { System.Threading.Tasks.Parallel.For(0, 1000000, (i, obj) => { foreach (var item in enums) { var a = item.GetDescriptionByConcurrentDictionary(); } }); }); } private List<Enum> GetTestEnums() { List<Enum> res = new List<Enum>(); res.Add(EnumMutliFTest.T1); res.Add(EnumMutliFTest.T2); res.Add(EnumMutliFTest.T3); res.Add(EnumMutliFTest.T4); res.Add(EnumMutliFTest.T5); res.Add(EnumMutliFTest.T6); res.Add(EnumMutliFTest.T7); res.Add(EnumMutliFTest.T8); res.Add(EnumMutliFTest.T9); res.Add(EnumMutliFTest.T10); res.Add(EnumMutliFTest.T11); res.Add(EnumMutliFTest.T12); res.Add(EnumMutliFTest.T13); res.Add(EnumMutliFTest.T14); res.Add(EnumMutliFTest.T15); res.Add(EnumMutliFTest.T16); res.Add(EnumMutliFTest.T17); res.Add(EnumMutliFTest.T18); res.Add(EnumMutliFTest.T19); res.Add(EnumMutliFTest.T20); res.Add(EnumMutliFTest.T21); res.Add(EnumMutliFTest.T22); res.Add(EnumMutliFTest.T23); res.Add(EnumMutliFTest.T24); res.Add(EnumMutliFTest.T25); res.Add(EnumMutliFTest.T26); res.Add(EnumMutliFTest.T27); res.Add(EnumMutliFTest.T28); res.Add(EnumMutliFTest.T29); res.Add(EnumMutliFTest.T30); res.Add(EnumMutliFTest.T31); res.Add(EnumMutliFTest.T32); res.Add(EnumMutliFTest.T33); res.Add(EnumMutliFTest.T34); res.Add(EnumMutliFTest.T35); res.Add(EnumMutliFTest.T36); res.Add(EnumMutliFTest.T37); res.Add(EnumMutliFTest.T38); res.Add(EnumMutliFTest.T3); res.Add(EnumMutliFTest.T18); res.Add(EnumMutliFTest2.T21); res.Add(EnumMutliFTest2.T22); res.Add(EnumMutliFTest2.T23); res.Add(EnumMutliFTest2.T24); res.Add(EnumMutliFTest2.T25); res.Add(EnumMutliFTest2.T26); res.Add(EnumMutliFTest2.T27); res.Add(EnumMutliFTest2.T28); res.Add(EnumMutliFTest2.T29); res.Add(EnumMutliFTest2.T210); res.Add(EnumMutliFTest2.T211); res.Add(EnumMutliFTest2.T212); res.Add(EnumMutliFTest2.T213); res.Add(EnumMutliFTest2.T214); res.Add(EnumMutliFTest2.T215); res.Add(EnumMutliFTest2.T216); res.Add(EnumMutliFTest2.T217); res.Add(EnumMutliFTest2.T218); res.Add(EnumMutliFTest2.T219); res.Add(EnumMutliFTest2.T220); res.Add(EnumMutliFTest2.T221); res.Add(EnumMutliFTest2.T222); res.Add(EnumMutliFTest2.T223); res.Add(EnumMutliFTest2.T224); res.Add(EnumMutliFTest2.T225); res.Add(EnumMutliFTest2.T226); res.Add(EnumMutliFTest2.T227); res.Add(EnumMutliFTest2.T228); res.Add(EnumMutliFTest2.T229); res.Add(EnumMutliFTest2.T230); res.Add(EnumMutliFTest2.T231); res.Add(EnumMutliFTest2.T232); res.Add(EnumMutliFTest2.T233); res.Add(EnumMutliFTest2.T234); res.Add(EnumMutliFTest2.T235); res.Add(EnumMutliFTest2.T236); res.Add(EnumMutliFTest2.T237); res.Add(EnumMutliFTest2.T238); res.Add(EnumMutliFTest2.T23); res.Add(EnumMutliFTest2.T218); return res; } public enum EnumMutliFTest { [System.ComponentModel.Description("DT1")] T1, [System.ComponentModel.Description("DT2")] T2, [System.ComponentModel.Description("DT3")] T3, [System.ComponentModel.Description("DT4")] T4, [System.ComponentModel.Description("DT5")] T5, [System.ComponentModel.Description("DT6")] T6, [System.ComponentModel.Description("DT7")] T7, [System.ComponentModel.Description("DT8")] T8, [System.ComponentModel.Description("DT9")] T9, [System.ComponentModel.Description("DT10")] T10, [System.ComponentModel.Description("DT11")] T11, [System.ComponentModel.Description("DT12")] T12, [System.ComponentModel.Description("DT13")] T13, [System.ComponentModel.Description("DT14")] T14, [System.ComponentModel.Description("DT15")] T15, [System.ComponentModel.Description("DT16")] T16, [System.ComponentModel.Description("DT17")] T17, [System.ComponentModel.Description("DT18")] T18, [System.ComponentModel.Description("DT19")] T19, [System.ComponentModel.Description("DT20")] T20, [System.ComponentModel.Description("DT21")] T21, [System.ComponentModel.Description("DT22")] T22, [System.ComponentModel.Description("DT23")] T23, [System.ComponentModel.Description("DT24")] T24, [System.ComponentModel.Description("DT25")] T25, [System.ComponentModel.Description("DT26")] T26, [System.ComponentModel.Description("DT27")] T27, [System.ComponentModel.Description("DT28")] T28, [System.ComponentModel.Description("DT29")] T29, [System.ComponentModel.Description("DT30")] T30, [System.ComponentModel.Description("DT31")] T31, [System.ComponentModel.Description("DT32")] T32, [System.ComponentModel.Description("DT33")] T33, [System.ComponentModel.Description("DT34")] T34, [System.ComponentModel.Description("DT35")] T35, [System.ComponentModel.Description("DT36")] T36, [System.ComponentModel.Description("DT37")] T37, [System.ComponentModel.Description("DT38")] T38, } public enum EnumMutliFTest2 { [System.ComponentModel.Description("DT21")] T21, [System.ComponentModel.Description("DT22")] T22, [System.ComponentModel.Description("DT23")] T23, [System.ComponentModel.Description("DT24")] T24, [System.ComponentModel.Description("DT25")] T25, [System.ComponentModel.Description("DT26")] T26, [System.ComponentModel.Description("DT27")] T27, [System.ComponentModel.Description("DT28")] T28, [System.ComponentModel.Description("DT29")] T29, [System.ComponentModel.Description("DT210")] T210, [System.ComponentModel.Description("DT211")] T211, [System.ComponentModel.Description("DT212")] T212, [System.ComponentModel.Description("DT213")] T213, [System.ComponentModel.Description("DT214")] T214, [System.ComponentModel.Description("DT215")] T215, [System.ComponentModel.Description("DT216")] T216, [System.ComponentModel.Description("DT217")] T217, [System.ComponentModel.Description("DT218")] T218, [System.ComponentModel.Description("DT219")] T219, [System.ComponentModel.Description("DT220")] T220, [System.ComponentModel.Description("DT221")] T221, [System.ComponentModel.Description("DT222")] T222, [System.ComponentModel.Description("DT223")] T223, [System.ComponentModel.Description("DT224")] T224, [System.ComponentModel.Description("DT225")] T225, [System.ComponentModel.Description("DT226")] T226, [System.ComponentModel.Description("DT227")] T227, [System.ComponentModel.Description("DT228")] T228, [System.ComponentModel.Description("DT229")] T229, [System.ComponentModel.Description("DT230")] T230, [System.ComponentModel.Description("DT231")] T231, [System.ComponentModel.Description("DT232")] T232, [System.ComponentModel.Description("DT233")] T233, [System.ComponentModel.Description("DT234")] T234, [System.ComponentModel.Description("DT235")] T235, [System.ComponentModel.Description("DT236")] T236, [System.ComponentModel.Description("DT237")] T237, [System.ComponentModel.Description("DT238")] T238, } //['d?end?] [Flags] public enum EnumGender { None, [System.ComponentModel.Description("男")] Male, [System.ComponentModel.Description("女")] Female, Other, } }
3.輔助測(cè)試類TestHelper.cs
public static class TestHelper { /// <summary> /// 執(zhí)行一個(gè)方法并返回執(zhí)行時(shí)間間隔 /// </summary> public static TimeSpan InvokeAndGetTimeSpan(Action call) { Stopwatch sw = new Stopwatch(); sw.Start(); call(); sw.Stop(); return sw.Elapsed; } /// <summary> /// 執(zhí)行一個(gè)方法并Console輸出實(shí)際執(zhí)行間隔(豪秒) /// </summary> [Conditional("DEBUG")] public static void InvokeAndWriteTimeSpan(Action call) { Console.WriteLine("TimeSpan:{0:N4}ms", InvokeAndGetTimeSpan(call).TotalMilliseconds); } /// <summary> /// 執(zhí)行一個(gè)方法并返回托管內(nèi)存使用大小(可能內(nèi)存回收會(huì)導(dǎo)致不準(zhǔn)確) /// </summary> public static long InvokeAndGetMemoryUsed(Action call) { var start = GC.GetTotalMemory(false); call(); return GC.GetTotalMemory(false) - start; } /// <summary> /// 執(zhí)行一個(gè)方法并Console輸出托管內(nèi)存使用大小(字節(jié)) /// </summary> [Conditional("DEBUG")] public static void InvokeAndWriteMemoryUsed(Action call) { Console.WriteLine("MemoryUsed:{0:N4}KB", InvokeAndGetMemoryUsed(call) / 1024F); } /// <summary> /// 執(zhí)行一個(gè)方法并Console輸出:實(shí)際執(zhí)行間隔(豪秒);托管內(nèi)存使用大小(可能內(nèi)存回收會(huì)導(dǎo)致不準(zhǔn)確) /// </summary> [Conditional("DEBUG")] public static void InvokeAndWriteAll(Action call) { Stopwatch sw = new Stopwatch(); sw.Start(); var start = GC.GetTotalMemory(false); call(); var end = GC.GetTotalMemory(false); sw.Stop(); Console.WriteLine("TimeSpan:{0:N4}ms", sw.ElapsedMilliseconds); Console.WriteLine("MemoryUsed:{0:N4}KB", (end - start) / 1024F); Console.WriteLine("CollectionCount(0):{0:N}", GC.CollectionCount(0)); } }
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