Dapper實用教程

本文轉載自查看原文 2017-08-07 09:31 3267 dapper/ Dapper

Dapper是什么？

　　Dpper是一款.Net平台簡單（Simple）的對象映射庫，並且Dapper擁有着“微型ORM之王”的稱號。就速度而言與手寫ADO.NET SqlDateReader相同。ORM是Object Relational Mapper的縮寫，代表着數據庫與編程語言之間的映射。

　　Dapper的基本特性是通過擴展IDbConnection 接口，並為其提供查詢數據庫的方法。

Dapper是如何工作的？

　　將大象裝冰箱總共分三步，Dapper也是如此。

創建IDBConnection對象（例如：SqlConnection）
編寫用於CRUD的Sql語句
將Sql語句當作參數純如執行操作的方法

安裝

　　通過NuGet安裝：https://www.nuget.org/packages/Dapper

　　PM> Install-Package Dapper

方法表

　　Dapper會用多個方法去擴展IDBConnection接口

Execute
Query
QueryFirst
QueryFirstOrDefault
QuerySingle
QuerySingleOrDefault
QueryMultiple

string sqlInvoices = "SELECT * FROM Invoice;";
string sqlInvoice = "SELECT * FROM Invoice WHERE InvoiceID = @InvoiceID;";
string sp = "EXEC Invoice_Insert";

using (var connection = My.ConnectionFactory())
{
    var invoices = connection.Query<Invoice>(sqlInvoices).ToList();
    var invoice = connection.QueryFirstOrDefault(sqlInvoice, new {InvoiceID = 1});
    var affectedRows = connection.Execute(sp, new { Param1 = "Single_Insert_1" }, commandType: CommandType.StoredProcedure);
}

參數表

　　有多種不同的方式給“查詢（例如：select）”和“執行（例如：delete、update、insert）”方法傳遞參數

Anonymous
Dynamic
List
String

// 匿名類對象（相對比較常用）
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();

結果集

　　查詢方法的返回值可以映射成多種類型

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

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();
}

Utilities

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);

執行非查詢語句

描述

你可以從任意實現IDbConnection的類對象中調用Dapper的擴展方法“Execute”。它能夠執行一條命令（Command）一次或者多次，並返回受影響的行數。這個方法通常用來執行：

Stored Procedure
INSERT statement
UPDATE statement
DELETE statement

參數

下面表格中顯示了Execute方法的不同參數

名稱	描述
sql	要執行的sql語句文本
param	command的參數
transaction	事務
commandTimeout	command超時時間
commandType	command類型

示例：執行存儲過程

單次

執行存儲過程一次

string sql = "EXEC Invoice_Insert";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure); My.Result.Show(affectedRows); }

多次

執行存儲過程多次，數組中的每條數據都執行一次

string sql = "EXEC Invoice_Insert";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new[] { new {Kind = InvoiceKind.WebInvoice, Code = "Many_Insert_1"}, new {Kind = InvoiceKind.WebInvoice, Code = "Many_Insert_2"}, new {Kind = InvoiceKind.StoreInvoice, Code = "Many_Insert_3"} }, commandType: CommandType.StoredProcedure ); My.Result.Show(affectedRows); }

示例：執行插入

單次

執行插入語句一次

string sql = "INSERT INTO Invoice (Code) Values (@Code);";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}); My.Result.Show(affectedRows); }

多次

執行多次，數組中的每條數據都執行一次

string sql = "INSERT INTO Invoice (Code) Values (@Code);";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new[] { new {Kind = InvoiceKind.WebInvoice, Code = "Many_Insert_1"}, new {Kind = InvoiceKind.WebInvoice, Code = "Many_Insert_2"}, new {Kind = InvoiceKind.StoreInvoice, Code = "Many_Insert_3"} } ); My.Result.Show(affectedRows); }

示例：執行Update

單次

執行Update語句一次

string sql = "UPDATE Invoice SET Code = @Code WHERE InvoiceID = @InvoiceID";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new {InvoiceID = 1, Code = "Single_Update_1"}); My.Result.Show(affectedRows); }

多次

執行多次，數組中的每條數據都執行一次。

string sql = "UPDATE Invoice SET Code = @Code WHERE InvoiceID = @InvoiceID";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new[] { new {InvoiceID = 1, Code = "Many_Update_1"}, new {InvoiceID = 2, Code = "Many_Update_2"}, new {InvoiceID = 3, Code = "Many_Update_3"} }); My.Result.Show(affectedRows); }

示例：執行Delete

單次

執行Delete語句一次

string sql = "DELETE FROM Invoice WHERE InvoiceID = @InvoiceID";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new {InvoiceID = 1}); My.Result.Show(affectedRows); }

多次

執行多次，數組中的每條數據都執行一次

string sql = "DELETE FROM Invoice WHERE InvoiceID = @InvoiceID";

using (var connection = My.ConnectionFactory()) { connection.Open(); var affectedRows = connection.Execute(sql, new[] { new {InvoiceID = 1}, new {InvoiceID = 2}, new {InvoiceID = 3} }); }

Dapper Query查詢

介紹

查詢方法（Query）是IDbConnection的擴展方法，它可以用來執行查詢（select）並映射結果到C#實體（Model、Entity）類

查詢結果可以映射成如下類型：

Anonymous 匿名類型
Strongly Typed 強類型
Multi-Mapping (One to One) 多映射一對一
Multi-Mapping (One to Many) 多映射一對多
Multi-Type 多類型

參數

下面表格中顯示了Query方法的不同參數

名稱	描述
sql	要執行的sql語句文本
param	command的參數
transaction	事務
buffered	True to buffer readeing the results of the query (default = true). 翻譯不來。。。
commandTimeout	command超時時間
commandType	command類型

示例 - 匿名查詢

Raw SQL query can be executed using Query method and map the result to a dynamic list.

直接執行SQL語句字符串，然后將結果映射成 dynamic類型的List中

string sql = "SELECT * FROM Invoice;";

using (var connection = My.ConnectionFactory()) { connection.Open(); var invoices = connection.Query(sql).ToList(); My.Result.Show(invoices); }

示例 - 強類型查詢（最常用）

直接執行SQL語句字符串，然后將結果映射成強類型類型的List中

string sql = "SELECT * FROM Invoice;";

using (var connection = My.ConnectionFactory()) { connection.Open(); var invoices = connection.Query<Invoice>(sql).ToList(); My.Result.Show(invoices); }

示例 - 多映射查詢 (One to One)

Raw SQL query can be executed using Query method and map the result to a strongly typed list with a one to one relation.（沒太理解）

直接執行SQL語句字符串，然后將結果用一對一的關系映射成強類型類型的List中

string sql = "SELECT * FROM Invoice AS A INNER JOIN InvoiceDetail AS B ON A.InvoiceID = B.InvoiceID;";

using (var connection = My.ConnectionFactory()) { connection.Open(); var invoices = connection.Query<Invoice, InvoiceDetail, Invoice>( sql, (invoice, invoiceDetail) => { invoice.InvoiceDetail = invoiceDetail; return invoice; }, splitOn: "InvoiceID") .Distinct() .ToList(); My.Result.Show(invoices); }

示例 - 查詢多映射 (One to Many)

Raw SQL query can be executed using Query method and map the result to a strongly typed list with a one to many relations.

直接執行SQL語句字符串，然后將結果用一對多的關系映射成強類型類型的List中

string sql = "SELECT * FROM Invoice AS A INNER JOIN InvoiceItem AS B ON A.InvoiceID = B.InvoiceID;";

using (var connection = My.ConnectionFactory()) { connection.Open(); var invoiceDictionary = new Dictionary<int, Invoice>(); var invoices = connection.Query<Invoice, InvoiceItem, Invoice>( sql, (invoice, invoiceItem) => { Invoice invoiceEntry; if (!invoiceDictionary.TryGetValue(invoice.InvoiceID, out invoiceEntry)) { invoiceEntry = invoice; invoiceEntry.Items = new List<InvoiceItem>(); invoiceDictionary.Add(invoiceEntry.InvoiceID, invoiceEntry); } invoiceEntry.Items.Add(invoiceItem); return invoiceEntry; }, splitOn: "InvoiceID") .Distinct() .ToList(); My.Result.Show(invoices); }

示例 - Query Multi-Type

Raw SQL query can be executed using Query method and map the result to a list of different types.

string sql = "SELECT * FROM Invoice;";

using (var connection = My.ConnectionFactory()) { connection.Open(); var invoices = new List<Invoice>(); using (var reader = connection.ExecuteReader(sql)) { var storeInvoiceParser = reader.GetRowParser<StoreInvoice>(); var webInvoiceParser = reader.GetRowParser<WebInvoice>(); while (reader.Read()) { Invoice invoice; switch ((InvoiceKind) reader.GetInt32(reader.GetOrdinal("Kind"))) { case InvoiceKind.StoreInvoice: invoice = storeInvoiceParser(reader); break; case InvoiceKind.WebInvoice: invoice = webInvoiceParser(reader); break; default: throw new Exception(ExceptionMessage.GeneralException); } invoices.Add(invoice); } } My.Result.Show(invoices); }

參考文章：

dapper toturial http://dapper-tutorial.net/dapper

http://dapper-tutorial.net/query

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