ORM 轻量级框架 Dapper（介绍） _轻量级

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Dapper是什么？Dapper是.net 一个简单的对象映射，就速度而言，他是轻量数据 Orm 之王，他和Ado.net的DataReader一样快。ORM是对象关系映射器，负责数据库和编程语言之间的映射。
Dapper 继承了IDbConnection，通过扩展数据库查询方法进行数据库查询
Dapper可与任何数据库提供程序使用，没有特定的数据库实现。
Dapper怎样工作？主要分三个过程：

创建一个IDbConnection 对象
编写CRUD操作语句
将操作语句作为参数，传递给Execute 方法

安装
Dapper通过Negut进行安装:https://www.nuget.org/packages/Dapper

PM> Install-Package Dapper

方法dapper使用多种方法扩展IDbConnection接口

Execute
Query
QueryFirst
QueryFirstOrDefault
QuerySingle
QuerySingleOrDefault
QueryMultiple

string sqlOrderDetails = "SELECT TOP 5 * FROM OrderDetails; "; string sqlOrderDetail = "SELECT * FROM OrderDetails WHERE OrderDetailID = @OrderDetailID; "; string sqlCustomerInsert = "INSERT INTO Customers (CustomerName) Values (@CustomerName); "; using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools())) { var orderDetails = connection.Query< OrderDetail> (sqlOrderDetails).ToList(); var orderDetail = connection.QueryFirstOrDefault< OrderDetail> (sqlOrderDetail, new {OrderDetailID = 1}); var affectedRows = connection.Execute(sqlCustomerInsert,new {CustomerName = "Mark"}); Console.WriteLine(orderDetails.Count); Console.WriteLine(affectedRows); FiddleHelper.WriteTable(orderDetails); FiddleHelper.WriteTable(new List< OrderDetail> () { orderDetail }); }

参数执行和查询可以使用多种不同类型的参数

Anonymous
Dynamic
List
String

// Anonymous var affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure); // Dynamic DynamicParameters parameter = new DynamicParameters(); parameter.Add("@Kind", InvoiceKind.WebInvoice, DbType.Int32, ParameterDirection.Input); parameter.Add("@Code", "Many_Insert_0", DbType.String, ParameterDirection.Input); parameter.Add("@RowCount", dbType: DbType.Int32, direction: ParameterDirection.ReturnValue); connection.Execute(sql, parameter, commandType: CommandType.StoredProcedure); int rowCount = parameter.Get< int> ("@RowCount"); // List connection.Query< Invoice> (sql, new {Kind = new[] {InvoiceKind.StoreInvoice, InvoiceKind.WebInvoice}}).ToList(); // String connection.Query< Invoice> (sql, new {Code = new DbString {Value = "https://www.songbingjia.com/android/Invoice_1", IsFixedLength = false, Length = 9, IsAnsi = true}}).ToList();

结果查询方法返回的结果可以映射为不同类型

Anonymous
Strongly Typed
Multi-Mapping
Multi-Result
Multi-Type

string sqlOrderDetails = "SELECT TOP 10 * FROM OrderDetails; "; using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools())) { var anonymousList = connection.Query(sqlOrderDetails).ToList(); var orderDetails = connection.Query< OrderDetail> (sqlOrderDetails).ToList(); Console.WriteLine(anonymousList.Count); Console.WriteLine(orderDetails.Count); FiddleHelper.WriteTable(orderDetails); FiddleHelper.WriteTable(connection.Query(sqlOrderDetails).FirstOrDefault()); }

实用工具

Async
Buffered
Transaction
Stored Procedure

// Async connection.QueryAsync< Invoice> (sql)// Buffered connection.Query< Invoice> (sql, buffered: false)// Transaction using (var transaction = connection.BeginTransaction()) { var affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure, transaction: transaction); transaction.Commit(); }// Stored Procedure var affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure);

【ORM 轻量级框架 Dapper（介绍）】