强大的拉姆表达式转Sql 类库 – SqlSugar 隐藏功能之Lambda

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所属分类:.NET技术
摘要

1、Lambda to sql 一直是ORM中最难的功能之一,如果有现成的解析库那么自已写一个ORM难度将大大降低


使用场景

1、Lambda to sql 一直是ORM中最难的功能之一,如果有现成的解析库那么自已写一个ORM难度将大大降低

2、通过Lambda作为KEY进行缓存操作,特别是仓储模式想要拿到表达式进行通用查询缓存 则需要用到表达式解析

3、学习爱好者,如果能够较深入的理Lambda如何去解成Sql,那么你对Lambda的理解将会更上一个层次,而不仅仅在使用上

 

优点

SqlSugar除了有自带的ORM功能,还是一款强大的拉姆达解析器  ,并且是市场上独有 的拉姆达转Sql类库 

SqlSugar不仅小巧并且性能非常的好,毫不逊色于Dapper 甚至更加的优秀  ,至于性能别看其他人的测评 非常不靠谱,自个用了才知道,自个测了才知道

1、高性能  表达式解析速度远超EF 

2、功能非常完整 ,并且是产品级的解析类库,支持各种模式的解析

3、小巧你只要引用SqlSugar一个DLL就能使用 解析各种数据库 、支持Sql函数 、支持常用原生函数

 

安装

.NET CORE / NET5   Nuget SqlSugarCore

.NET 4.5   Nuget SqlSugar 

.NET 4.0 Nuget SqlSuagr 4.x

 

入门

我们先来看一下例子

static void Main(string[] args) {  var age = 11;  Expression<Func<Test, bool>> exp = a => a.id == age; //表达式  SqlServerExpressionContext expContext = new SqlServerExpressionContext();//创建解析对象  expContext.Resolve(exp, ResolveExpressType.WhereSingle);//开始解析  var value = expContext.Result.GetString();//( [id] = @id0 )  var pars = expContext.Parameters;// @id:11 }  

 下面是调试结果:

强大的拉姆表达式转Sql 类库 - SqlSugar 隐藏功能之Lambda

 

 通过上面的例子就能够完美的将表达式转换成Sql语句

 

教程案例

1、如何创建 ExpressionContext 解析对象

 我们可以通过SqlSugar.DbType进行区分数据库 并且进行实例化

ExpressionContext expContext=null; switch (dbtype) { case DbType.MySql: expContext = new MySqlExpressionContext(); break; case DbType.SqlServer: expContext = new SqlServerExpressionContext(); break; case DbType.Sqlite: expContext = new SqliteExpressionContext(); break; case DbType.Oracle: expContext = new OracleExpressionContext(); break; case DbType.PostgreSQL: expContext = new PostgreSQLExpressionContext(); break; case DbType.Dm: expContext = new DmExpressionContext(); break; case DbType.Kdbndp: expContext = new KdbndpExpressionContext(); break; default: throw new Exception("不支持");

 

 2、Where条件的解析

基本和写EF一样常用的都会支持

Expression<Func<DataTestInfo2, bool>> exp = it => it.Bool2== b.Value; expContext.Resolve(exp, ResolveExpressType.WhereSingle); var value = expContext.Result.GetString(); var pars = expContext.Parameters; //( [Bool2] = @Bool20 )

我们在写一个Like的例子

Expression<Func<Student, bool>> exp = it => it.Name.Contains(schoolData.Name); ExpressionContext expContext = new ExpressionContext(); expContext.Resolve(exp, ResolveExpressType.WhereMultiple); var value = expContext.Result.GetString(); var pars = expContext.Parameters; //([it].[Name] like '%'+@MethodConst0+'%') 

bool类型的解析是ORM解析的难点中的难点,情况多种多样

Expression<Func<DataTestInfo2, bool>> exp = it => it.Bool1&&it.Bool1; SqlServerExpressionContext expContext = new SqlServerExpressionContext(); expContext.Resolve(exp, ResolveExpressType.WhereSingle); var value = expContext.Result.GetString(); var pars = expContext.Parameters; //( ( [Bool1]=1 ) AND ( [Bool1]=1 ) )

多样化的bool解释的支持

Expression<Func<Student, bool>> exp = it =>true&& it.Name != null; ExpressionContext expContext = new ExpressionContext(); expContext.Resolve(exp, ResolveExpressType.WhereSingle); var value = expContext.Result.GetString(); var pars = expContext.Parameters; //(( 1 = 1 ) AND( [Name] IS NOT NULL ))

多表查询的支持,在多表查询中我们是需要加前缀的比如 我们想要 it.id 而不是id

  Expression<Func<Student, bool>> exp = it => (it.Id > 1 && it.Name != name || it.Id == 1) || it.Name == WhereConst.name;   ExpressionContext expContext = new ExpressionContext();   expContext.Resolve(exp, ResolveExpressType.WhereMultiple);   var value = expContext.Result.GetString();   var pars = expContext.Parameters; //(((( [it].[Id] > @Id0 ) AND ( [it].[Name] <> @Name1 )) OR ( [it].[Id] = @Id2 )) OR ( [it].[Name] = @Name3 ))

 

3、如何解析Select

支持实体类解析、查询单个字段解析、匿名对象解析

Expression<Func<DataTestInfo2, DataTestInfo2>> exp =it => new DataTestInfo2() {  Bool1=it.Bool1 , Bool2=it.Bool2 }; ExpressionContext expContext = new ExpressionContext(); expContext.IsSingle = false; expContext.Resolve(exp, ResolveExpressType.SelectSingle); var selectorValue = expContext.Result.GetString(); var pars = expContext.Parameters; //[Bool1] AS [Bool1] , [Bool2] AS [Bool2] 

 

Expression<Func<Student, School, object>> exp = (it, school) => new { Name = "a", Id = it.Id / 2, SchoolId = school.Id }; ExpressionContext expContext = new ExpressionContext(); expContext.IsSingle = false; expContext.Resolve(exp, ResolveExpressType.SelectMultiple); var selectorValue = expContext.Result.GetString(); // @constant0 AS [Name] , ( [it].[Id] / @Id1 ) AS [Id] , [school].[Id] AS [SchoolId] 

 

3、字段名称的解析

例如orderby(it=>it.Name) 像这种我们就需要拿到Name

Expression<Func<Student, object>> exp = it => it.Name; ExpressionContext expContext = GetContext(); expContext.Resolve(exp, ResolveExpressType.FieldSingle); var selectorValue = expContext.Result.GetString(); //Name

统计单 个字段

Expression<Func<Student, object>> exp = it =>SqlFunc.AggregateAvg(it.Id); ExpressionContext expContext = GetContext(); expContext.Resolve(exp, ResolveExpressType.FieldMultiple); var selectorValue = expContext.Result.GetString(); //AVG([it].[Id])

 

4、Sql函数的支持 

Expression<Func<Student, bool>> exp = it => (it.Name.Contains("a")? 1:2)==1; SqlServerExpressionContext expContext = new SqlServerExpressionContext(); expContext.Resolve(exp, ResolveExpressType.WhereSingle); var value = expContext.Result.GetString(); var pars = expContext.Parameters; //(( CASE  WHEN  ([Name] like '%'+@MethodConst0+'%')  THEN @MethodConst1  ELSE @MethodConst2 END ) = @Const3 )

支持的C#函数:

.ToString  .Contains  .Length

.ToLower  .ToUpper  .ToSubstring 

.Equals    .HasValue  .Replace

.EndsWith  .StartsWith  .Trim

.HasValue  .Value  .AddDay  .Date

和常用的Convert.ToInt32等等 

 

SqlFunc.函数

SqlFunc函数下面包含了大量SQL函数  

 SqlFunc.IF(st.Id > 1)      .Return(st.Id)      .ElseIF(st.Id == 1)      .Return(st.SchoolId).End(st.Id) //等于Case when

 

5、其它功能

5.1 支持特性比如我表名和实体名不一样我们也可以实现

SqlServerExpressionContext expContext = new SqlServerExpressionContext(); expContext.MappingTables.Add(typeof(Student).Name,"OA_STUDENT")

列名也非常容易

SqlServerExpressionContext expContext = new SqlServerExpressionContext(); expContext.MappingColumns.Add("Id","ID",typeof(Student).Name)

 

5.2 支持子查询

Expression<Func<Test, bool>> exp = a => SqlFunc.Subqueryable<Sutdent>().Where(it => it.testId == a.id).Select(it => it.id) == 1); var expContext = new SqlServerExpressionContext();  expContext.Resolve(exp, ResolveExpressType.WhereSingle); var value = expContext.Result.GetString(); var pars = expContext.Parameters;

 

6、自已动手创建ORM

通上面的学习你们想写出下面的语法应该相当容易了 

 var oneClass = db.Queryable<Order, OrderItem, Custom>((o, i, c) => o.Id == i.OrderId&& o.CustomId == c.Id)) .Where(o=>o.id==1)  .Where((o,i)=>i.xx==1)  .OrderBy(o=>o.Id) .Select((o,i,c)=> new ViewOrder  {           Id=SqlFunc.GetSelfAndAutoFill(o.Id),// o.*           CustomName=c.Name   //[c].[Name] AS [CustomName] }).ToList()

实现上面的功能 总共用到Where的解析、列的解析和Select的解析

1、下面3个用到Where的解析

(o, i, c) => o.Id == i.OrderId&& o.CustomId == c.Id)  o=>o.id==1 (o,i)=>i.xx==1

 2、下面1个用到列的解析

o=>o.Id

 3、下面1个用到Select的解析

(o,i,c)=> new ViewOrder  {           Id=SqlFunc.GetSelfAndAutoFill(o.Id),// o.*           CustomName=c.Name   //[c].[Name] AS [CustomName] }

 

  

源码下载:

你们的赞或者你们的 star 就是 开源者的动力 ,开源不容易和气生财 

https://github.com/sunkaixuan/SqlSugar     

 

彩蛋:

下一篇文章 我会介绍如何使用 SqlSugar 实现WebFirst模式开发代码,领先CodeFirst和DbFirst的设计和开发理念,也我十多年开发经验的汇总