生成唯一文件名不同方法
测试一
private void TestUnid()
{
Parallel.For(1, 100, (i) =>
{
var fileName = DateTime.Now.ToString("yyyyMMddHHmmss");
Random rnd = new Random();
Console.WriteLine("fileName=" + fileName + rnd.Next(1000, 100000));
});
}
输出：
fileName=2016102614594469808
fileName=2016102614594469808
fileName=2016102614594469808
...重复的
fileName=201610261459446330
fileName=201610261459446330
fileName=201610261459446330
fileName=201610261459446330
...重复的
fileName=2016102614594411511
fileName=2016102614594411511
fileName=2016102614594411511
fileName=2016102614594411511
结论：可以看出有大量重复的文件名，原因是在并行时，Random用的默认种子是一样的，所以得到的随机数重复，
测试二
private static int iCount;
private void TestUnid()
{
Parallel.For(1, 100, (i) =>
{
var fileName = DateTime.Now.ToString("yyyyMMddHHmmss");
Random rnd = new Random();
Interlocked.Increment(ref iCount);
Console.WriteLine("fileName=" + fileName + rnd.Next(10, 10000)+"_"+iCount.ToString());
});
}
输出：
fileName=201610261502447236_1
fileName=201610261502447236_3
fileName=201610261502447236_5
fileName=201610261502447236_6
fileName=201610261502447236_8
fileName=201610261502447236_9
fileName=201610261502447236_10
fileName=201610261502447236_11
fileName=201610261502447236_12
fileName=201610261502447236_13
fileName=201610261502447236_14
fileName=201610261502447236_15
fileName=201610261502447236_16
fileName=201610261502447236_17
fileName=201610261502447236_4
fileName=201610261502447236_19
fileName=201610261502447236_18
fileName=201610261502447236_21
fileName=201610261502447236_22
fileName=201610261502447236_23
fileName=201610261502447236_24
fileName=201610261502447236_25
fileName=201610261502447236_26
fileName=201610261502447236_27
fileName=201610261502447236_28
fileName=201610261502447236_29
fileName=201610261502447236_2
fileName=201610261502447236_31
fileName=201610261502447236_7
fileName=201610261502447236_33
fileName=201610261502447236_34
fileName=201610261502447236_35
fileName=201610261502447236_36
fileName=201610261502447236_20
fileName=201610261502447236_30
fileName=201610261502447236_32
fileName=201610261502447236_37
fileName=201610261502447236_41
fileName=201610261502447236_43
fileName=201610261502447236_44
fileName=201610261502447236_45
fileName=201610261502447236_46
fileName=201610261502447236_47
fileName=201610261502447236_48
fileName=201610261502447236_49
fileName=201610261502447236_50
fileName=201610261502447236_51
fileName=201610261502447236_42
fileName=201610261502447236_53
fileName=201610261502447236_54
fileName=201610261502447236_55
fileName=201610261502447236_56
fileName=201610261502447236_57
fileName=201610261502447236_58
fileName=201610261502447236_59
fileName=201610261502447236_60
fileName=201610261502447236_61
fileName=201610261502447236_62
fileName=201610261502447236_63
fileName=201610261502447236_64
fileName=201610261502447236_65
fileName=201610261502447236_39
fileName=201610261502447236_66
fileName=201610261502447236_40
fileName=201610261502447236_68
fileName=201610261502447236_38
fileName=201610261502447236_67
fileName=201610261502447236_69
fileName=201610261502447236_52
fileName=201610261502447759_73
fileName=201610261502447759_74
fileName=201610261502447759_75
fileName=201610261502447759_76
fileName=201610261502447759_77
fileName=201610261502447759_78
fileName=201610261502447759_79
fileName=201610261502447759_80
fileName=201610261502447759_81
fileName=201610261502447759_70
fileName=201610261502447759_82
fileName=201610261502447759_84
fileName=201610261502447759_85
fileName=201610261502447759_86
fileName=201610261502447759_87
fileName=201610261502447759_83
fileName=201610261502447759_71
fileName=201610261502447759_88
fileName=201610261502447759_72
fileName=201610261502447759_90
fileName=201610261502447759_91
fileName=201610261502447759_92
fileName=201610261502447759_93
fileName=201610261502447759_94
fileName=201610261502447759_89
fileName=201610261502447759_95
fileName=201610261502447759_96
fileName=201610261502447759_97
fileName=201610261502453063_98
fileName=201610261502453063_99
结论：可以看出没有重复的，但在这里随机数也还是没用，不重复是靠iCount来控制的
测试三
private void TestUnid()
{
Parallel.For(1, 100, (i) =>
{
var fileName = DateTime.Now.ToString("yyyyMMddHHmmss");
Random rnd = new Random(Guid.NewGuid().GetHashCode());
Console.WriteLine("fileName=" + fileName + rnd.Next(10, 1000000));
});
}
输出：
fileName=20161026151027973826
fileName=20161026151027179385
fileName=20161026151027445591
fileName=20161026151027847317
fileName=20161026151027606114
fileName=20161026151027929078
fileName=20161026151027304060
fileName=20161026151027690171
fileName=20161026151027611574
fileName=20161026151027479382
fileName=20161026151027721579
fileName=2016102615102738259
fileName=2016102615102734888
fileName=20161026151027315651
fileName=20161026151027724837
fileName=20161026151027547173
fileName=20161026151027314361
fileName=20161026151027235100
fileName=20161026151027463807
fileName=20161026151027912844
fileName=20161026151027260381
fileName=20161026151027984721
fileName=20161026151027293500
fileName=20161026151027123672
fileName=20161026151027597298
fileName=20161026151027885499
fileName=20161026151027408799
fileName=20161026151027196271
fileName=20161026151027472364
fileName=20161026151027844070
fileName=20161026151027789116
fileName=20161026151027643316
fileName=20161026151027502302
fileName=20161026151027448703
fileName=2016102615102751061
fileName=20161026151027151289
fileName=20161026151027366014
fileName=20161026151027517970
fileName=20161026151027277171
fileName=20161026151027861437
fileName=20161026151027180729
fileName=20161026151027910238
fileName=20161026151027864665
fileName=20161026151027529615
fileName=20161026151027421393
fileName=20161026151027225208
fileName=20161026151027118632
fileName=20161026151027453933
fileName=20161026151027781073
fileName=20161026151027435784
fileName=20161026151027259237
fileName=20161026151027600569
fileName=20161026151027521430
fileName=20161026151027237649
fileName=20161026151027933160
fileName=20161026151027396719
fileName=20161026151027685772
fileName=20161026151027701230
fileName=20161026151027400333
fileName=20161026151027410161
fileName=20161026151027788633
fileName=20161026151027936531
fileName=20161026151027522519
fileName=20161026151027849716
fileName=20161026151027590020
fileName=20161026151027555132
fileName=20161026151027259429
fileName=20161026151027567186
fileName=20161026151027390216
fileName=20161026151027614342
fileName=2016102615102854752
fileName=20161026151028173374
fileName=20161026151028991435
fileName=2016102615102894246
fileName=20161026151028497667
fileName=20161026151028365669
fileName=20161026151028808273
fileName=20161026151028568480
fileName=20161026151028686578
fileName=20161026151028627480
fileName=20161026151028248219
fileName=20161026151028691944
fileName=201610261510284772
fileName=20161026151028346370
fileName=20161026151028817242
fileName=20161026151028340723
fileName=20161026151028236019
fileName=20161026151028638904
fileName=20161026151028248779
fileName=20161026151028123635
fileName=20161026151028344443
fileName=20161026151028699403
fileName=20161026151028349303
fileName=20161026151028118220
fileName=20161026151028232106
fileName=20161026151028185281
fileName=2016102615102891660
fileName=20161026151028933221
fileName=20161026151028167604
结论：这里面应该也是没有重复的，但有重复的可能，因为虽然Random的种子每次不一样了，但生成随机数还是有可能会有重复，但概率比较小了，
测试四
private static int iCount;
private void TestUnid()
{
Parallel.For(1, 100, (i) =>
{
var fileName = DateTime.Now.ToString("yyyyMMddHHmmss");
Interlocked.Increment(ref iCount);
Random rnd = new Random(Guid.NewGuid().GetHashCode());
Console.WriteLine("fileName=" + fileName + iCount.ToString().PadRight(4,'0')+rnd.Next(1, 10000).ToString().PadLeft(4,'0'));
});
}
输出：
fileName=2016102615421634001080
fileName=2016102615421633007073
fileName=2016102615421635000421
fileName=2016102615421636006721
fileName=2016102615421627005785
fileName=2016102615421638000321
fileName=2016102615421642003512
fileName=2016102615421641005752
fileName=2016102615421643008674
fileName=2016102615421644004218
fileName=2016102615421645008183
fileName=2016102615421646003962
fileName=2016102615421647000283
fileName=2016102615421648003970
fileName=2016102615421649005367
fileName=2016102615421651004208
fileName=2016102615421650001274
fileName=2016102615421652008767
fileName=2016102615421653000678
fileName=2016102615421654007918
fileName=2016102615421655002593
fileName=2016102615421656002064
fileName=2016102615421657009178
fileName=2016102615421658005146
fileName=2016102615421659006539
fileName=2016102615421660003764
fileName=2016102615421661008740
fileName=2016102615421640002590
fileName=2016102615421663000390
fileName=2016102615421664004351
fileName=2016102615421665000917
fileName=2016102615421666005014
fileName=2016102615421637000092
fileName=2016102615421639009017
fileName=2016102615421662001313
fileName=2016102615421667004809
fileName=2016102615421672006933
fileName=2016102615421673007296
fileName=2016102615421674009097
fileName=2016102615421675002749
fileName=2016102615421676006875
fileName=2016102615421677008682
fileName=2016102615421678005366
fileName=2016102615421669005274
fileName=2016102615421670002655
fileName=2016102615421679001878
fileName=2016102615421680004663
fileName=2016102615421681000694
fileName=2016102615421682007521
fileName=2016102615421683001165
fileName=2016102615421684007344
fileName=2016102615421685008041
fileName=2016102615421668002134
fileName=2016102615421686002166
fileName=2016102615421671003766
fileName=2016102615421687001968
fileName=2016102615421688007910
fileName=2016102615421689001718
fileName=2016102615421690003355
fileName=2016102615421691007049
fileName=2016102615421692006476
fileName=2016102615421693007589
fileName=2016102615421694003435
fileName=2016102615421695007512
fileName=2016102615421696006017
fileName=2016102615421697008858
fileName=2016102615421698007807
fileName=2016102615421699001709
结论：这个是没有重复的，生成的随机数种子也不同，而且带上iCount保证了唯一。
测试五
private void TestUnid()
{
Parallel.For(1, 100, (i) =>
{
//不用ToString("N"),默认的是"D",里面带"-"
var fileName = Guid.NewGuid().ToString("N");
Console.WriteLine("fileName=" + fileName);
});
}
输出：
fileName=48f5445240ab4e16b9243f833606c765
fileName=3001bccb4ecc4672a1492bf7ddb7b6aa
fileName=2a9091388671447b82dc38a8503d429e
fileName=3399220040c04d319774ed1891eddb2f
fileName=9716c75fd8a74ea38833b7fb126c32a2
fileName=e1062e22a2d4449395e39f86149bbfe8
fileName=8ab0e5fef7df44c29ee9a79a4f139630
fileName=e022a9af93b3451c9bf6fceb7e4a2c0b
fileName=4edfb58d071043dca5d574508696ed4a
fileName=a8b05d2ef92c422a8ebb128d0102af4d
fileName=5382d16c9eb140d192c7d083b05e19a9
fileName=14bde8b6f3cc42b2b3331c9c61a5d3f6
fileName=80f6848bbb224947a2b2326039f91050
fileName=dd3c8791bbbb4f17ba0910f67af857d6
fileName=35f348299803439b9e5588681d4e55bf
fileName=e6f208c012fc438d8d09c72a6272fc45
fileName=99371f05de894160a8ee6b8776aa5492
fileName=01336494f3804bdea8da71d552756052
fileName=82c35aa705a34c0cb1378f145eb4c69f
fileName=92315ae5910e41828296f0f468808a5d
fileName=f0f1e6ebaad6410aaa64e997a0f28b5a
fileName=477c9c50edc24c339e22ae997f8c8674
fileName=814f47f6b9ac47ed8fe9027bf4db9bde
fileName=8adc22da263941588a7644e65176682d
fileName=116ee790785847f7b9129f7fbf1f2ac2
fileName=227e6cf1bf334d0da3a57c46c655edcd
fileName=47b5fd5e03d84f4b945fa9d47a199174
fileName=900e240a183c461bba3c28e871341fb9
fileName=bbbd95ccd0b143dfbe5adc19292c0bf4
fileName=28450dfff97045c882f740a511b0d4fe
fileName=8ce2a10345f14bb987367653345e931d
fileName=7e90485d1dd84e638a68605883305afd
fileName=1d46823cef004254b4d4705ccaa94d6b
fileName=6c3d82c142954f48a754bf0a8e403812
fileName=1cd674231cb34a7f9c5d3595d0947daa
fileName=3ec4b8f1f4eb4b8897a0d369d8f8725e
......
这个应该也是没有重复的，利用的是Guid的唯一性，这种方法比较省事，但是不带时间信息在里面
所以，要生成真正唯一的文件名，要用最后二种方法
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