Dapper是一个简单的.NET对象映射器，在速度方面具有"小巧的信封 of Micro ORM"的头衔，几乎与使用原始的ADO.NET数据读取器一样快。ORM是一个对象关系映射器，它负责数据库和编程语言之间的映射。
Dapper通过扩展IDbConnection提供一些有用的扩展方法去查询您的数据库。
Dapper是如何工作的它可以分为三个步骤：
创建一个IDbConnection接口对象；编写一个查询SQL来执行CRUD操作；将查询SQL作为Execute方法的参数传递。 安装Dapper通过NuGet安装：https://www.nuget.org/packages/Dapper
PM> Install-Package Dapper 要求Dapper可以与任何数据库提供者一起工作，因为没有数据库特定的实现。
方法Dapper会用以下几个方法扩展您的IDbConnection接口：
ExecuteQueryQueryFirstQueryFirstOrDefaultQuerySingleQuerySingleOrDefaultQueryMultiple string sqlInvoices = "SELECT * FROM Invoice;";string sqlInvoice = "SELECT * FROM Invoice WHERE InvoiceID = @InvoiceID;";string sp = "EXEC Invoice_Insert";using (var connection = My.ConnectionFactory()){ // 执行普通SQL var invoices = connection.Query<Invoice>(sqlInvoices).ToList(); // 执行带参数的SQL var invoice = connection.QueryFirstOrDefault(sqlInvoice, new {InvoiceID = 1}); // 执行存储过程 var affectedRows = connection.Execute(sp, new { Param1 = "Single_Insert_1" }, commandType: CommandType.StoredProcedure);} 参数执行和查询方法可以用以下几种不同的方式使用参数：
匿名类型动态类型列表类型字符串类型 // Anonymousvar affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure);// DynamicDynamicParameters 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, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure);// Listconnection.Query<Invoice>(sql, new {Kind = new[] {InvoiceKind.StoreInvoice, InvoiceKind.WebInvoice}}).ToList();// Stringconnection.Query<Invoice>(sql, new {Code = new DbString {Value = "Invoice_1", IsFixedLength = false, Length = 9, IsAnsi = true}}).ToList(); 结果查询方法返回的结果可以映射到以下几种类型：
匿名类型强类型多映射多结果多类型 string sql = "SELECT * FROM Invoice;";using (var connection = My.ConnectionFactory()){ connection.Open(); var anonymousList = connection.Query(sql).ToList(); var invoices = connection.Query<Invoice>(sql).ToList();} 工具 异步缓冲事务存储过程 // Asyncconnection.QueryAsync<Invoice>(sql)// Bufferedconnection.Query<Invoice>(sql, buffered: false)// Transactionusing (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 Procedurevar affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure);