Entity FrameWork 是以ADO.net為基礎發展的ORM解決方案。

一、安裝Entity FrameWork框架

二、添加ADO.Net實體數據模型

三、EF插入數據

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){//獲取數據庫上下文對象testContext dbContext = new testContext();//創建數據實體employee emp = new employee{name = "yangs",passwd = "123",age = 18};dbContext.employee.Add(emp);//提交數據 dbContext.SaveChanges();Console.WriteLine(emp.id);Console.ReadKey();}} }

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四、EF刪除數據

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){//獲取idemployee emp = new employee{id = 18};//獲取數據庫上下文對象testContext dbContext = new testContext();//將實體添加到數據庫上下文 dbContext.employee.Attach(emp);//對數據刪除 dbContext.employee.Remove(emp);//保存 dbContext.SaveChanges();}} }

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五、EF修改數據

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){//準備實體employee emp = new employee{id = 11,name = "例子",passwd = "123",age = 44};//獲取數據庫上下文對象testContext dbContext = new testContext();//將實體添加到數據庫上下文 dbContext.employee.Attach(emp);dbContext.Entry(emp).State = System.Data.Entity.EntityState.Modified;dbContext.SaveChanges();}} }

六、EF 查詢數據

1.簡單查詢

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();var list = dbContext.employee;foreach (var item in list){Console.WriteLine(item.name);}Console.ReadKey();}} }

2.where 查詢條件

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();var list = dbContext.employee.Where(p => p.id > 5);foreach (var item in list){Console.WriteLine(item.name);}Console.ReadKey();}} }

2. skip(10) => 逃過10條數據，take(10) => 獲取10條數據

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();var list = dbContext.employee.Skip(1).Take(2);foreach (var item in list){Console.WriteLine(item.name);}Console.ReadKey();}} }

?3. orderBy 排序

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();//降序var list = dbContext.employee.OrderByDescending(p => p.id);foreach (var item in list){Console.WriteLine(item.name);}Console.ReadKey();}} }

4. select 查詢某幾個字段

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();//降序var list = dbContext.employee.Select(p => new { p.id, p.name }).Where(p => p.id > 5);foreach (var item in list){Console.WriteLine(item.id+" -- "+item.name);}Console.ReadKey();}} }

5. EF高級寫法

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();//降序var list = from o in dbContext.employee where o.id > 5 select o; foreach (var item in list){Console.WriteLine(item.id+" -- "+item.name);}Console.ReadKey();}} }

join 聯合查詢

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();//降序var list = from e in dbContext.employeejoin i in dbContext.employeeInfoon e.id equals i.emp_idwhere e.id > 5 select new {e, i.content};}} }

?七、延遲加載

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;namespace EFDemo {class Program{static void Main(string[] args){testContext dbContext = new testContext();//降序var list = dbContext.employee.ToList();foreach (var item in list){}}} }

toList()轉換為本地內存數據級別，會請求數據。如果沒有toList()，則當數據遍歷的時候請求。

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轉載于:https://www.cnblogs.com/yang-2018/p/10222140.html

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