EF简单增删改查

using(var db = new Entities())
{
    //数据操作
}

    UserInfo user = new UserInfo()
    {
        UserName = "zhangsan1",
        UserPass = "123123"
    };
    db.UserInfo.Add(user);

    user = new UserInfo()
    {
        UserID = 4, //根据主键删除
        UserName = "zhangsan",
        UserPass = "12312311111"
    };
    db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Deleted;

    user = new UserInfo()
    {
        UserID = 13 //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

    //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 == 14
                    select v).Single();
        db.UserInfo.Remove(user);
        db.SaveChanges();
    }

    user = new UserInfo()
    {
        UserID = 12,
        UserName = "zhangsan",
        UserPass = "987654"
    };
    db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Modified;

    user = new UserInfo()
    {
        UserID = 12,
        UserName = "zhangsan"
    };
    db.UserInfo.Attach(user);
    db.Entry<UserInfo>(user).Property<string>(v => v.UserName).IsModified = true;

    using (var db = new Entities())
    {
        var user = (from v in db.UserInfo
                    where v.UserName == "zhangsan"
                    select v).Single();
        user.UserPass = "123456";
        db.SaveChanges();
    }

    var users = db.UserInfo;
    foreach (var v in users)
    {
        ObjectDumper.Write(v);//打印实体
    }

    using (var db = new Entities())
    {
        var user = db.UserInfo.Find(12);
        ObjectDumper.Write(user);
    }

using(var db = new Entities())
{
    //新增
    UserInfo user = new UserInfo()
    {
        UserName = "zhangsan1",
        UserPass = "123123"
    };
    db.UserInfo.Add(user);
                
    //删除
    user = new UserInfo()
    {
        UserID = 4, //根据主键删除
        UserName = "zhangsan",
        UserPass = "12312311111"
    };
    db.Entry<UserInfo>(user).State = System.Data.Entity.EntityState.Deleted;

    //删除 方法2
    user = new UserInfo()
    {
        UserID = 13 //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 == 14
                select v).Single();
    db.UserInfo.Remove(user);
    db.SaveChanges();

    //修改
    user = new UserInfo()
    {
        UserID = 12,
        UserName = "zhangsan",
        UserPass = "987654"
    };
    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(12);
    ObjectDumper.Write(user);

    //保存更新到数据库
    db.SaveChanges();
}