. Net: sequence number of the Extensible document number generator (to prevent duplication)

ArticleDirectory

• Seed Table Design
• Running result

Background

In my previous article ". Net: extensible document number generator + simple interpreter", I introduced a simple document numbering framework. A friend left a message asking how to implement"Sequence number, and cannot be repeated", This article uses the framework introduced in the previous article to address this issue.

Train of Thought sequence number = last sequence number + step size

According to the formula above, the problem can be resolved as follows: how to obtain the sequence number of the last time? You can obtain the sequence number in either of the following ways:

1. 1. Scan the document table to find the latest record.
   2. The seed table is introduced. The seed table records the latest sequence number.

Because the generated sequence numbers cannot be repeated, there is a concurrency requirement here. To maximize the concurrency, I choose 2 (Introduce a seed table).

Concurrent processing can be selected: Pessimistic lock or optimistic lock. For simplicity, I choosePessimistic lock.

Implementation Code Download: http://yunpan.cn/q5kmuta3qgpct. Seed Table Design

 1   Create  Table   [  DBO  ] . [  Codeseeds  ]  (  2       [  ID  ]      Uniqueidentifier   Not   Null  ,  3       [ Key  ]     Nvarchar ( 500 ) Not   Null  ,  4       [  Value  ]   Int                Not   Null  ,  5       Primary  Key   Clustered ( [  ID  ]   ASC  )  6 );

Seedcoderuleprovider. CS

 1   Using  System;  2   Using  System. Collections. Generic;  3   Using System. LINQ;  4   Using  System. text;  5   Using  System. Threading. tasks;  6   7   Using  System. Transactions;  8   Using  System. Text. regularexpressions;  9   Using System. Data. entity. Infrastructure;  10   11   Namespace  Entitycoderuledemo  12   {  13       Public   Class  Seedcoderuleprovider: icoderuleprovider  14   {  15           Private   Readonly  Int  _ Width;  16   17           Public Seedcoderuleprovider ( Int  Width)  18   {  19 _ Width = Width;  20   }  21   22           Public  String Generate ( Object  Entity)  23   {  24               Return Getseedvalue (Entity). tostring (). padleft (_ width, '  0  '  );  25   }  26   27           Protected  Virtual   String Getkey ( Object  Entity)  28   {  29               Return  Entity. GetType (). fullname;  30   }  31   32           Private   Int Getseedvalue ( Object Entity)  33   {  34               Try  35   {  36                   VaR Value = 0  ;  37                   VaR Key = This  . Getkey (entity );  38   39                  Using ( VaR TS = New  Transactionscope (transactionscospontion. requiresnew,  40                       New Transactionoptions {isolationlevel = Isolationlevel. repeatableread }))  41   {  42                       Using ( VaR Context = New  Testcontext ()) 43   {  44                           VaR Seed = context. codeseeds. Where (x => X. Key = Key). firstordefault ();  45                           If (Seed = Null  )  46   {  47 Seed = New Codeseed {id = guid. newguid (), Key = key, value =-1  };  48   Context. codeseeds. Add (SEED );  49   }  50   51 Seed. Value ++ ;  52 Value = Seed. value;  53   Context. savechanges ();  54  }  55   56   TS. Complete ();  57   }  58   59                   Return  Value;  60   }  61               Catch  (Dbupdateexception)  62  {  63                   Return   This  . Getseedvalue (entity );  64   }  65   }  66   67           Public   Static Seedcoderuleprovider seedcoderuleproviderfactory ( String  Literal)  68  {  69               VaR Match = New RegEx ( "  ^ <Seed (:(? <Width>. *?)?> $  "  ). Match (literal );  70   71               VaR Width = match. Groups [ "  Width  "  ]. Value;  72  73               Return   New Seedcoderuleprovider ( String . Isnullorempty (width )? 5 : Int  . Parse (width ));  74   }  75   }  76 }

Program. CS

 1   Using  System; 2   Using  System. Collections. Generic;  3   Using  System. LINQ;  4   Using  System. text;  5   Using  System. Threading. tasks;  6   7   Using  System. Text. regularexpressions; 8   9   Namespace  Entitycoderuledemo  10   {  11       Class  Program  12   {  13           Static   Void Main ( String  [] ARGs)  14  {  15 Coderuleinterpreter. registproviderfactory ( New RegEx ( "  ^ <Seed (:(? <Width>. *?)?> $  "  ), Seedcoderuleprovider. seedcoderuleproviderfactory );  16   17               VaR Employeecode = Coderuleinterpreter  18 . Interpret ( " Prefix _ <date: yyyy_mm_dd >_< attribute: namepinyin >_< seed: 6>  "  )  19 . Generate ( New Employee {namepinyin = "  Duangw  "  });  20   21   Console. writeline (employeecode );  22   }  23  }  24 }

Running result

Remarks

There are write business requirements that will force the continuity of numbers or random numbers. For these two requirements, you also need to develop a separate provider and have the opportunity to write articles again.