Dapper

Dapper 第一篇简单介绍

2019-05-31  本文已影响0人  懒懒的程序员一枚

短小精悍的

什么是小巧玲珑?

Dapper是.NET的简单对象映射器,在速度方面拥有微型ORM之王的标题,几乎与使用原始ADO.NET数据读取器一样快。 ORM是一个对象关系映射器,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来扩展IDbConnection。

Dapper如何工作:
  • 创建一个IDbConnection对象。
  • 编写查询以执行CRUD操作。
  • 将查询作为Execute方法中的参数传递。
安装

Dapper通过NuGet安装: https //www.nuget.org/packages/Dapper

PM> Install-Package Dapper
需求

Dapper可以与任何数据库提供程序一起使用,因为没有特定于DB的实现。

方法

Dapper将使用多种方法扩展您的IDbConnection接口:

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

执行和查询方法可以使用多种不同方式的参数:

// 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,
    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 = "Invoice_1", IsFixedLength = 

结果

query方法返回的结果可以映射到多种类型:

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());
}
常用类型
// 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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