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Dapper官方教程翻译1：Dapper是什么？

2018年12月20日 16:07:28 Day_and_Night_2017 阅读数：108

 

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

1.  
   string sqlOrderDetails = "SELECT TOP 5 * FROM OrderDetails;";
2.  
   string sqlOrderDetail = "SELECT * FROM OrderDetails WHERE OrderDetailID = @OrderDetailID;";
3.  
   string sqlCustomerInsert = "INSERT INTO Customers (CustomerName) Values (@CustomerName);";
4.  
    
5.  
   using (var connection = new SqlCeConnection("Data Source=SqlCe_W3Schools.sdf"))
6.  
   {
7.  
   var orderDetails = connection.Query<OrderDetail>(sqlOrderDetails).ToList();
8.  
   var orderDetail = connection.QueryFirstOrDefault<OrderDetail>(sqlOrderDetail, new {OrderDetailID = 1});
9.  
   var affectedRows = connection.Execute(sqlCustomerInsert, new {CustomerName = "Mark"});
10.  
     
11.  
    Console.WriteLine(orderDetails.Count);
12.  
    Console.WriteLine(affectedRows);
13.  
     
14.  
    FiddleHelper.WriteTable(orderDetails);
15.  
    FiddleHelper.WriteTable(new List<OrderDetail>() { orderDetail });
16.  
    }

Dapper参数：

• Anonymous
• Dynamic
• List
• String

1.  
   // Anonymous
2.  
   var affectedRows = connection.Execute(sql,
3.  
   new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"},
4.  
   commandType: CommandType.StoredProcedure);
5.  
    
6.  
   // Dynamic
7.  
   DynamicParameters parameter = new DynamicParameters();
8.  
    
9.  
   parameter.Add("@Kind", InvoiceKind.WebInvoice, DbType.Int32, ParameterDirection.Input);
10.  
    parameter.Add("@Code", "Many_Insert_0", DbType.String, ParameterDirection.Input);
11.  
    parameter.Add("@RowCount", dbType: DbType.Int32, direction: ParameterDirection.ReturnValue);
12.  
     
13.  
    connection.Execute(sql,
14.  
    parameter,
15.  
    commandType: CommandType.StoredProcedure);
16.  
     
17.  
    int rowCount = parameter.Get<int>("@RowCount");
18.  
     
19.  
    // List
20.  
    connection.Query<Invoice>(sql, new {Kind = new[] {InvoiceKind.StoreInvoice, InvoiceKind.WebInvoice}}).ToList();
21.  
    // String
22.  
    connection.Query<Invoice>(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

1.  
   string sqlOrderDetails = "SELECT TOP 10 * FROM OrderDetails;";
2.  
    
3.  
   using (var connection = new SqlCeConnection("Data Source=SqlCe_W3Schools.sdf"))
4.  
   {
5.  
   var anonymousList = connection.Query(sqlOrderDetails).ToList();
6.  
   var orderDetails = connection.Query<OrderDetail>(sqlOrderDetails).ToList();
7.  
    
8.  
   Console.WriteLine(anonymousList.Count);
9.  
   Console.WriteLine(orderDetails.Count);
10.  
     
11.  
    FiddleHelper.WriteTable(orderDetails);
12.  
     
13.  
    FiddleHelper.WriteTable(connection.Query(sqlOrderDetails).FirstOrDefault());
14.  
    }

Dapper其他辅助工具

• Async
• Buffered
• Transaction
• Stored Procedure

1.  
   // Async
2.  
   connection.QueryAsync<Invoice>(sql)
3.  
    
4.  
   // Buffered
5.  
   connection.Query<Invoice>(sql, buffered: false)
6.  
    
7.  
   // Transaction
8.  
   using (var transaction = connection.BeginTransaction())
9.  
   {
10.  
    var affectedRows = connection.Execute(sql,
11.  
    new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"},
12.  
    commandType: CommandType.StoredProcedure,
13.  
    transaction: transaction);
14.  
     
15.  
    transaction.Commit();
16.  
    }
17.  
     
18.  
    // Stored Procedure
19.  
    var affectedRows = connection.Execute(sql,
20.  
    new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"},
21.  
    commandType: CommandType.StoredProcedure);