Dapper

原文：Dapper Tutorial ，译者：Esofar

什么是Dapper

Dapper是一个简单的.NET对象映射器，在速度方面具有"King 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：

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：

// 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,
    new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"},
    commandType: CommandType.StoredProcedure);

// List
connection.Query<Invoice>(sql, new {Kind = new[] {InvoiceKind.StoreInvoice, InvoiceKind.WebInvoice}}).ToList();

// String
connection.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：

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

// 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);

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