目錄
背景
在應用程序的特定情況下,我們必須以DataTable對象的形式獲取結果。該應用程序正在使用Oracle數據庫和Entity Framework EDMX。我們必須使用現有的數據庫上下文實例從未映射的共享視圖中選擇數據。爲此,我實際上爲DbContext對象編寫了一些擴展方法,如下所述。
擴展方式
我們將創建DbContext同時考慮Entity Framework和Entity Framework Core的擴展方法。擴展方法將通過以下方式調用:
- SQL查詢字符串
- 可選DbParameter對象,如果使用參數化查詢
讓我們開始編寫代碼。
實體框架(Entity Framework)
using System.Data;
using System.Data.Common;
using System.Data.Entity;
public static class DbContextExtensions
{
/*
* need
Only EntityFramework
*/
public static DataTable DataTable(this DbContext context, string sqlQuery,
params DbParameter[] parameters)
{
DataTable dataTable = new DataTable();
DbConnection connection = context.Database.Connection;
DbProviderFactory dbFactory = DbProviderFactories.GetFactory(connection);
using (var cmd = dbFactory.CreateCommand())
{
cmd.Connection = connection;
cmd.CommandType = CommandType.Text;
cmd.CommandText = sqlQuery;
if (parameters != null)
{
foreach (var item in parameters)
{
cmd.Parameters.Add(item);
}
}
using (DbDataAdapter adapter = dbFactory.CreateDataAdapter())
{
adapter.SelectCommand = cmd;
adapter.Fill(dataTable);
}
}
return dataTable;
}
}
實體框架核心(Entity Framework Core)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.Common;
using Microsoft.EntityFrameworkCore;
public static class DbContextExtensions
{
/*
* need
Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Relational
*/
public static DataTable DataTable(this DbContext context,
string sqlQuery, params DbParameter[] parameters)
{
DataTable dataTable = new DataTable();
DbConnection connection = context.Database.GetDbConnection();
DbProviderFactory dbFactory = DbProviderFactories.GetFactory(connection);
using (var cmd = dbFactory.CreateCommand())
{
cmd.Connection = connection;
cmd.CommandType = CommandType.Text;
cmd.CommandText = sqlQuery;
if (parameters != null)
{
foreach (var item in parameters)
{
cmd.Parameters.Add(item);
}
}
using (DbDataAdapter adapter = dbFactory.CreateDataAdapter())
{
adapter.SelectCommand = cmd;
adapter.Fill(dataTable);
}
}
return dataTable;
}
}
我試圖將代碼放到一個普通項目中,這實際上取決於Microsoft.EntityFrameworkCore.Relational。默認情況下,它會自動包含任何提供程序DLL,比如Microsoft.EntityFrameworkCore.SqlServer。
使用擴展方法
使用常規查詢
var db = new MopDb();
DataTable allUser = db.DataTable("SELECT * FROM [dbo].[tbl_test_role]");
使用參數化查詢
var db = new MopDb();
/*stored procedure*/
DataTable searchUser = db.DataTable(
"EXEC sp_test_role @name = @paramName",
new SqlParameter("paramName", SqlDbType.NVarChar) { Value = "sa" }
);
/*select query*/
DataTable likeUser = db.DataTable(
"SELECT * FROM [dbo].[tbl_test_role] WHERE [name] LIKE '%' + @paramName +'%'",
new SqlParameter("paramName", SqlDbType.NVarChar) { Value = "a" }
);
我們正在執行存儲過程和查詢,我相信函數也將起作用。
不同數據庫的DbParameter名稱
- SqlServer:SqlParameter
- Oracle:OracleParameter
- MySql的:MySqlParameter
- PostgreSQL的:NpgsqlParameter
將源代碼與SQL-Server Db一起使用
Db對象
創建Db對象
CREATE TABLE [dbo].[tbl_test_role] (
[id] INT IDENTITY (1, 1) NOT NULL,
[name] NVARCHAR (50) NOT NULL,
[details] NVARCHAR (150) NULL,
PRIMARY KEY CLUSTERED ([id] ASC)
);
INSERT INTO [dbo].[tbl_test_role] (name)
VALUES ('admin'), ('sa'), ('user');
CREATE PROCEDURE sp_test_role @name nvarchar(30)
AS
BEGIN
SELECT * FROM [dbo].[tbl_test_role]
WHERE [name] = @name;
END;
如果需要,可以刪除Db對象
DROP TABLE [dbo].[tbl_test_role];
DROP PROCEDURE sp_test_role;
解決方案和項目
這是Visual Studio 2017解決方案:
- WithEf 是.NET Framework 4.5
- WithEfCore 是.NET Core 2.2
更改連接字符串
WithEf中的App.config:
<connectionStrings>
<add name="MopDbConnection" connectionString="Data Source=10.10.15.13\DB002;
Initial Catalog=TESTDB; PASSWORD=dhaka; USER ID=FSTEST;"
providerName="System.Data.SqlClient" />
</connectionStrings>
WithEfCore中的appsettings.json:
"ConnectionStrings": {
"MopDbConnection": "server=10.10.15.13\\DB002;database=TESTDB;
user id=FSTEST;password=dhaka"
}