EFCore扩展Update方法(实现 Update User SET Id = Id + 1)

• 源码地址(github)

前言

1. EFCore在操作更新的时候往往需要先查询一遍数据，再去更新相应的字段，如果针对批量更新的话会很麻烦，效率也很低。
2. 目前github上 EFCore.Extentions 项目,实现批量更新挺方便的，但是针对 Update User SET Id = Id + 1 这种操作还是没有解决
3. 本文主要就是扩展自更新Update

实现原理

1. 先根据IQuaryable 获取到SQL语句

         private  static  readonly  TypeInfo  QueryCompilerTypeInfo  =  typeof ( QueryCompiler ) . GetTypeInfo ();
         private  static  readonly  FieldInfo  QueryCompilerField  =  typeof ( EntityQueryProvider ) . GetTypeInfo () . DeclaredFields . First ( x  =>  x . Name  ==  "_queryCompiler" );
         private  static  readonly  FieldInfo  QueryModelGeneratorField  =  QueryCompilerTypeInfo . DeclaredFields . First ( x  =>  x . Name  ==  "_queryModelGenerator" );
         private  static  readonly  FieldInfo  DataBaseField  =  QueryCompilerTypeInfo . DeclaredFields . Single ( x  =>  x . Name  ==  "_database" );
         private  static  readonly  PropertyInfo  DatabaseDependenciesField  =  typeof ( Database ) . GetTypeInfo () . DeclaredProperties . Single ( x  =>  x . Name  ==  "Dependencies" );

         ///   < summary >
         ///  将query 转化为sql语句
         ///   </ summary >
         ///   < typeparam  name = " TEntity " ></ typeparam >
         ///   < param  name = " query " ></ param >
         ///   < returns ></ returns >
         internal  static  string  ToSql < TEntity >( this  IQueryable < TEntity >  query )  where  TEntity  :  class
         {
             var  queryCompiler  =  ( QueryCompiler ) QueryCompilerField . GetValue ( query . Provider );
             var  modelGenerator  =  ( QueryModelGenerator ) QueryModelGeneratorField . GetValue ( queryCompiler );
             var  queryModel  =  modelGenerator . ParseQuery ( query . Expression );
             var  database  =  ( IDatabase ) DataBaseField . GetValue ( queryCompiler );
             var  databaseDependencies  =  ( DatabaseDependencies ) DatabaseDependenciesField . GetValue ( database );
             var  queryCompilationContext  =  databaseDependencies . QueryCompilationContextFactory . Create ( false );
             var  modelVisitor  =  ( RelationalQueryModelVisitor ) queryCompilationContext . CreateQueryModelVisitor ();

             modelVisitor . CreateQueryExecutor < TEntity >( queryModel );
             string  sql  =  modelVisitor . Queries . First () . ToString ();
             return  sql ;
         }

2. 把获取的查询语句的，From之前的语句砍掉，然后拼接

         public  static  ( string ,  string )  GetBatchSql < T >( IQueryable < T >  query )  where  T  :  class ,  new ()
         {
             string  sqlQuery  =  query . ToSql ();
             string  tableAlias  =  sqlQuery . Substring ( 8 ,  sqlQuery . IndexOf ( "]" )  -  8 );
             int  indexFROM  =  sqlQuery . IndexOf ( Environment . NewLine );
             string  sql  =  sqlQuery . Substring ( indexFROM ,  sqlQuery . Length  -  indexFROM );
             sql  =  sql . Contains ( "{" )  ?  sql . Replace ( "{" ,  "{{" )  :  sql ;  // Curly brackets have to escaped:
             sql  =  sql . Contains ( "}" )  ?  sql . Replace ( "}" ,  "}}" )  :  sql ;  // https://github.com/aspnet/EntityFrameworkCore/issues/8820
             return  ( sql ,  tableAlias );
         }

3. 根据传入的表达式Expression<Func<T,bool> 生成(Update [a] SET) 之后要更新的部分.列如：Expression<Func<T,bool> expression=a=>a.Id == a.Id + 1 生成[a].[Id]=[a].[Id]+parm_0 pram_0=1

通过分析Expression的节点[NodeType]来生成相应的操作符，递归拼接sql语句和参数

         public  static  void  CreateUpdateBody ( string  Param ,  Expression  expression ,  ref  StringBuilder  sb ,  ref  List < SqlParameter >  sp )
         {
             if  ( expression  is  BinaryExpression  binaryExpression )
             {
                 CreateUpdateBody ( Param ,  binaryExpression . Left ,  ref  sb ,  ref  sp );

                 switch  ( binaryExpression . NodeType )
                 {
                     case  ExpressionType . Add :
                         sb . Append ( " +" );
                         break ;
                     case  ExpressionType . Divide :
                         sb . Append ( " /" );
                         break ;
                     case  ExpressionType . Multiply :
                         sb . Append ( " *" );
                         break ;
                     case  ExpressionType . Subtract :
                         sb . Append ( " -" );
                         break ;
                     case  ExpressionType . And :
                         sb . Append ( " ," );
                         break ;
                     case  ExpressionType . AndAlso :
                         sb . Append ( " ," );
                         break ;
                     case  ExpressionType . Or :
                         sb . Append ( " ," );
                         break ;
                     case  ExpressionType . OrElse :
                         sb . Append ( " ," );
                         break ;
                     case  ExpressionType . Equal :
                         sb . Append ( " =" );
                         break ;
                     default :  break ;
                 }

                 CreateUpdateBody ( Param ,  binaryExpression . Right ,  ref  sb ,  ref  sp );
             }

             if  ( expression  is  ConstantExpression  constantExpression )
             {
                 var  parmName  =  $"param_ { sp . Count } " ;
                 sp . Add ( new  SqlParameter ( parmName ,  constantExpression . Value ));
                 sb . Append ( $" @ { parmName } " );
             }

             if  ( expression  is  MemberExpression  memberExpression )
             {
                 sb . Append ( $" { Param } .[ { memberExpression . Member . Name } ]" );
             }
         }

4. 最后执行生成SQL语句，详情请看源码github

5. 调用

         static  void  Main ( string []  args )
         {
             using  ( var  context  =  new  TestContext ())
             {
                 var  list  =  context . User . Select < UserModel >() . ToList ();

                 var  user1  =  context . User . AsNoTracking () . FirstOrDefault ( x  =>  x . Id  ==  2 );

                 Console . WriteLine ( $"-----------Before Update --------------------" );
                 Console . WriteLine ( $" { user1 . Id } : { user1 . Name } : { user1 . RoleId } " );

                 context . User . Where ( x  =>  x . Id  ==  2 ) . RestValue ( x  =>  x . Name  ==  ( x . Name  +  " Add Bob" )  &&  x . RoleId  ==  ( x . RoleId  +  1 ));

                 var  user2  =  context . User . AsNoTracking () . FirstOrDefault ( x  =>  x . Id  ==  2 );

                 Console . WriteLine ( $"-----------After Update --------------------" );
                 Console . WriteLine ( $" { user2 . Id } : { user2 . Name } : { user2 . RoleId } " );
             }
             Console . WriteLine ( $"------------结束--------------------" );
             Console . ReadLine ();
         }

6. 生成的SQL如下

     UPDATE [x] SET x.[Name] =x.[Name] + @param_0 ,x.[RoleId] =x.[RoleId] + @param_1
     FROM [User] AS [x]
     WHERE [x].[Id] = 2