Dapper官方教程翻译1：Dapper是什么？

什么是Dapper？

Dapper是.NET的一个简单的对象映射器，在速度上拥有微ORM之王的头衔，并且几乎与使用原始ADO.NET数据读取器的速度一样快。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通过提供有用的扩展方法来查询数据库，从而扩展IDbConnection。

 

如何使用Dapper？

 

使用Dapper只需要三步：

1.创建IDbConnecton对象

2.写一个CURD语句

3.将语句作为参数传递给Execute方法。

 

Dapper安装：

 

使用NuGet命令：Install-Package Dapper

 

数据库要求：

 

只要是提供了数据库Provider的数据库，就可以用Dapper。

 

Dapper扩展方法：

 

• 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 SqlCeConnection("Data Source=SqlCe_W3Schools.sdf"))
{
	var orderDetails = connection.Query(sqlOrderDetails).ToList();
	var orderDetail = connection.QueryFirstOrDefault(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 });
}

 

Dapper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("@RowCount");

// List
connection.Query(sql, new {Kind = new[] {InvoiceKind.StoreInvoice, InvoiceKind.WebInvoice}}).ToList();
// String
connection.Query(sql, new {Code = new DbString {Value = "Invoice_1", IsFixedLength = false, Length = 9, IsAnsi = true}}).ToList();

 

Dapper执行结果

 

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

string sqlOrderDetails = "SELECT TOP 10 * FROM OrderDetails;";

using (var connection = new SqlCeConnection("Data Source=SqlCe_W3Schools.sdf"))
{
	var anonymousList = connection.Query(sqlOrderDetails).ToList();
	var orderDetails = connection.Query(sqlOrderDetails).ToList();

	Console.WriteLine(anonymousList.Count);
	Console.WriteLine(orderDetails.Count);

	FiddleHelper.WriteTable(orderDetails);

	FiddleHelper.WriteTable(connection.Query(sqlOrderDetails).FirstOrDefault());
}

 

Dapper其他辅助工具

 

• Async
• Buffered
• Transaction
• Stored Procedure

// Async
connection.QueryAsync(sql)

// Buffered
connection.Query(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);