基本用法（CRUD）
1.插入：
// Create entity context
MyTest2Entities mt = new MyTest2Entities(); // Create an instance of SClass
SClass sc = new SClass(); sc.AddTime = DateTime.Now; sc.Name = "Class 1"; // Insert the instance into database
mt.SClasses.Add(sc); int count = mt.SaveChanges(); Console.WriteLine(count.ToString());
2.修改：
// Create entity context
MyTest2Entities mt = new MyTest2Entities(); // Create an instance need modified
SClass sc = new SClass(); sc.Id = 2; sc.Name = "Kyle"; sc.AddTime = DateTime.Now; // Attach the entity need modified
mt.SClasses.Attach(sc); // Modify execute status
mt.Entry(sc).State = System.Data.Entity.EntityState.Modified; mt.SaveChanges();
3.查询：
#region Multiple record query MyTest2Entities mt = new MyTest2Entities(); var classes = from c in mt.SClasses where c.Id < 10
select c; foreach (var item in classes) { Console.WriteLine(item.Name); } #endregion
#region Single record query MyTest2Entities mt = new MyTest2Entities(); var single = (from c in mt.SClasses where c.Id == 1
select c).FirstOrDefault(); if (single != null) Console.WriteLine(single.Name); #endregion
4.删除：
MyTest2Entities mt = new MyTest2Entities(); SClass sc = new SClass(); sc.Id = 2; mt.SClasses.Attach(sc); mt.Entry(sc).State = System.Data.Entity.EntityState.Deleted; mt.SaveChanges();
获取主键：
// TestEntities 继承于 DbContext
using (var db = new TestEntities()) { var objectContext = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)db).ObjectContext; // Brand 是其中一个表
ObjectSet<Brand> set = objectContext.CreateObjectSet<Brand>(); //Act
IEnumerable<string> keyNames = set.EntitySet.ElementType.KeyMembers.Select(k => k.Name); Console.WriteLine("{0}", string.Join(",", keyNames.ToArray())); }
转载于:https://www.cnblogs.com/jizhiqiliao/p/10905614.html
版权声明：本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 举报，一经查实，本站将立刻删除。
发布者：全栈程序员-用户IM，转载请注明出处：https://javaforall.cn/100904.html原文链接：https://javaforall.cn
【正版授权，激活自己账号】： Jetbrains全家桶Ide使用，1年售后保障，每天仅需1毛
【官方授权 正版激活】： 官方授权 正版激活 支持Jetbrains家族下所有IDE 使用个人JB账号...
![业务架构师如何进阶成长[通俗易懂]](http://javaforall.cn/wp-content/themes/justnews/themer/assets/images/lazy.png)