ORM 輕量級框架 Dapper（介紹）

Dapper是什么？

Dapper是.net 一個簡單的對象映射，就速度而言，他是輕量數據 Orm 之王，他和Ado.net的DataReader一樣快。ORM是對象關系映射器，負責數據庫和編程語言之間的映射。

Dapper 繼承了IDbConnection，通過擴展數據庫查詢方法進行數據庫查詢

Dapper可與任何數據庫提供程序使用，沒有特定的數據庫實現。

Dapper怎樣工作？

   主要分三個過程：

• 　　創建一個IDbConnection 對象
• 　　編寫CRUD操作語句
• 　　將操作語句作為參數，傳遞給Execute 方法

安裝

Dapper通過Negut進行安裝:https://www.nuget.org/packages/Dapper

PM> Install-Package Dapper

 

方法

dapper使用多種方法擴展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 });
}

　

參數

執行和查詢可以使用多種不同類型的參數

• 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 = "Invoice_1", IsFixedLength = false, Length = 9, IsAnsi = true}}).ToList();

 

結果

查詢方法返回的結果可以映射為不同類型

• 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());
}

 

實用工具

• 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);