第一步：创建上下文对象
using(var db = new Entities())
{
//数据操作
}
新增
UserInfo user = new UserInfo()
{
UserName = "zhangsan1",
UserPass = ""
};
db.UserInfo.Add(user);
删除
user = new UserInfo()
{
UserID = , //根据主键删除
UserName = "zhangsan",
UserPass = ""
};
db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Deleted;
说明：此例中虽然指定了UserName和UserPass属性值，但是EF执行的时候只会根据主键UserID生成查询条件，所以只需要制定UserID即可。
删除 方法2
user = new UserInfo()
{
UserID = //根据主键删除
};
//Attach的实体事先不能已经在内存中,否则上下文会追踪到两个相同键名的实体
db.UserInfo.Attach(user);//将对象添加到EF管理容器中 ObjectStateManager
db.UserInfo.Remove(user);//将对象包装类状态标识为删除
删除 先查询-再删除
//先加载整个实体 再删除 执行了2次sql 效率略低
using (var db = new Entities())
{
var user = (from v in db.UserInfo
where v.UserID ==
select v).Single();
db.UserInfo.Remove(user);
db.SaveChanges();
}
修改
user = new UserInfo()
{
UserID = ,
UserName = "zhangsan",
UserPass = ""
};
db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Modified;
修改单个属性
user = new UserInfo()
{
UserID = ,
UserName = "zhangsan"
};
db.UserInfo.Attach(user);
db.Entry<UserInfo>(user).Property<string>(v => v.UserName).IsModified = true;
说明：将UserID=12的用户名称改为 zhangsan
修改单个实体 先查询-再修改
using (var db = new Entities())
{
var user = (from v in db.UserInfo
where v.UserName == "zhangsan"
select v).Single();
user.UserPass = "123456";
db.SaveChanges();
}
说明：将用户名为 zhangsan的用户 密码修改为：123456
查询所有实体
var users = db.UserInfo;
foreach (var v in users)
{
ObjectDumper.Write(v);//打印实体
}
查询单个实体 主键查询
using (var db = new Entities())
{
var user = db.UserInfo.Find();
ObjectDumper.Write(user);
}
说明：查询UserID=12的用户
备注：所有增删改操作都需要调用 db.SaveChanges() 方法，才能更新到数据库。
完整案例：
using(var db = new Entities())
{
//新增
UserInfo user = new UserInfo()
{
UserName = "zhangsan1",
UserPass = ""
};
db.UserInfo.Add(user); //删除
user = new UserInfo()
{
UserID = , //根据主键删除
UserName = "zhangsan",
UserPass = ""
};
db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Deleted; //删除 方法2
user = new UserInfo()
{
UserID = //根据主键删除
};
//Attach的实体事先不能已经在内存中,否则上下文会追踪到两个相同键名的实体
db.UserInfo.Attach(user);//将对象添加到EF管理容器中 ObjectStateManager
db.UserInfo.Remove(user);//将对象包装类状态标识为删除 //删除单个实体
//先加载整个实体 再删除 执行了2次sql 效率略低
user = (from v in db.UserInfo
where v.UserID ==
select v).Single();
db.UserInfo.Remove(user);
db.SaveChanges(); //修改
user = new UserInfo()
{
UserID = ,
UserName = "zhangsan",
UserPass = ""
};
db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Modified; //修改单个属性
db.UserInfo.Attach(user);
db.Entry<UserInfo>(user).Property<string>(v => v.UserName).IsModified = true; //修改单个实体
user = (from v in db.UserInfo
where v.UserName == "zhangsan"
select v).Single();
user.UserPass = "abcd";
db.SaveChanges(); //查询遍历
var users = db.UserInfo;
foreach (var v in users)
{
ObjectDumper.Write(v);
} //查询单个实体
user = db.UserInfo.Find();
ObjectDumper.Write(user); //保存更新到数据库
db.SaveChanges();
}