EF Core基础入门
1. 安装
此处使用的是SQL SERVER数据库，.Net 框架式 .Net Core 2.2，由于.Net core 2.2的Microsoft.AspNetCore.App已经集成了对SQL Server的 EF Core 框架，所以不必再进行安装
2. 实例教程
- 增加
#region 保存
///
/// 保存
///
public void Add()
{
User userModel = new User()
{
CreateTime = DateTime.Now,
UserGroup = "111111",
UserName = "小李",
UserNo = "8440"
};
var resultUserModel = _testContext.User.Add(userModel);
int i = _testContext.SaveChanges();
}
#endregion
#region 异步保存
///
/// 异步保存
///
public void AddAsync()
{
User userModel = new User()
{
CreateTime = DateTime.Now,
UserGroup = "111111",
UserName = "小李异步保存的",
UserNo = "8440"
};
var resultUserModel = _testContext.User.Add(userModel);
var result = _testContext.SaveChangesAsync();
}
#endregion
#region 批量增加
///
/// 批量增加
///
private void AddBulk()
{
List listUsers = new List();
for (int i = 0; i < 100000; i++)
{
Usergroup UsergroupModel = new Usergroup()
{
CreateTime = DateTime.Now,
GroupId = "111111" + i.ToString(),
GroupName = i.ToString()
};
listUsers.Add(UsergroupModel);
}
var sw = new Stopwatch();
sw.Start();
_testContext.Usergroup.AddRange(listUsers);
_testContext.SaveChanges();
sw.Stop();
var spanTime = sw.Elapsed.TotalSeconds;
//List listUsers = new List();
//for (int i = 0; i < 100000; i++)
//{
// User userModel = new User()
// {
// CreateTime = DateTime.Now,
// UserGroup = "111111",
// UserName = "小李",
// UserNo = i.ToString()
// };
// listUsers.Add(userModel);
//}
//var sw = new Stopwatch();
//sw.Start();
//_testContext.User.AddRange(listUsers);
//_testContext.SaveChanges();
//sw.Stop();
//var spanTime = sw.Elapsed.TotalSeconds;
}
#endregion
- 修改
#region 批量修改指定字段
///
/// 批量修改指定字段
///
private void UpdateBulk()
{
var modelList = _testContext.User.Where(s => s.UserId > 55002 && s.UserId < 105002).ToList();
// var modelList = _testContext.User.ToList();
foreach (var VARIABLE in modelList)
{
VARIABLE.UserNo = "2222222";
}
var sw = new Stopwatch();
sw.Start();
//方法一，自带的UpdateRange
_testContext.User.UpdateRange(modelList);
ViewBag.dataCount = _testContext.SaveChanges();
sw.Stop();
var spanTime = sw.Elapsed.TotalSeconds;
ViewBag.spanTime = spanTime;
}
#endregion
#region 修改
///
/// 修改
///
public int Update()
{
User userModel = new User()
{
CreateTime = DateTime.Now,
UserGroup = "111111",
UserName = "小李-22222修改的",
UserNo = "8440",
UserId = 55002
};
var resultUserModel = _testContext.User.Update(userModel);
int i = _testContext.SaveChanges();
return i;
}
#endregion
#region 修改指定字段
///
/// 修改指定字段
///
public int UpdatePart()
{
User userModel = new User()
{
CreateTime = DateTime.Now,
UserGroup = "113434534511",
UserName = "小李-22222修改的",
UserNo = "8440",
UserId = 55002
};
_testContext.Attach(userModel);
_testContext.Entry(userModel).Property(s => s.UserGroup).IsModified = true;
_testContext.Entry(userModel).Property(s => s.CreateTime).IsModified = false;
_testContext.Entry(userModel).Property(s => s.UserName).IsModified = false;
_testContext.Entry(userModel).Property(s => s.UserNo).IsModified = false;
int i = _testContext.SaveChanges();
return i;
}
#endregion
- 删除
#region 异步批量删除
///
/// 异步批量删除
///
///
/// 异步删除
///
///
/// 批量删除
///
private void RemoveBulk()
{
var userModel = _testContext.User.Take(1000).ToList();
var sw = new Stopwatch();
sw.Start();
_testContext.User.RemoveRange(userModel);
ViewBag.dataCount = _testContext.SaveChanges();
ViewBag.spanTime = sw.Elapsed.TotalSeconds;
}
#endregion
#region 删除
///
/// 删除
///
private void Remove()
{
var userModel = _testContext.User.FirstOrDefault();
var sw = new Stopwatch();
sw.Start();
_testContext.User.Remove(userModel);
ViewBag.dataCount = _testContext.SaveChanges();
ViewBag.spanTime = sw.Elapsed.TotalSeconds;
}
#endregion
- 各种查询，分页查询等
///
/// 动态条件分页查询
///
///
///
///
/// 查询-单表单个实体
///
private void GetModel()
{
Expression> predicate = s => s.UserId == 60159;
var model = _testContext.User.FirstOrDefault();
model = _testContext.User.Where(predicate).FirstOrDefault();
}
#endregion
#region 查询-单表列表
///
/// 查询-单表列表
///
private void GetModelList()
{
var model = _testContext.User.ToList();
}
#endregion
#region 查询-单表分页
///
/// 查询-单表分页
/// 当前页码
/// 每页显示记录数
///
private void GetModelPage(int page, int pageSize)
{
int skipCount = 0;
if (page > 1)
{
skipCount = (page - 1) * pageSize;
}
var sw = new Stopwatch();
sw.Start();
List users = _testContext.User.Skip(skipCount).Take(pageSize).ToList();
sw.Stop();
ViewBag.spanTime = sw.Elapsed.TotalSeconds;
ViewBag.dataCount = users.Count;
}
#endregion
#region 查询-多表左右连接
///
/// 查询-多表左右连接
///
private object GetModelJoinList()
{
var sw = new Stopwatch();
sw.Start();
//Join
//var result = (from user in _testContext.User
// join myUsergroup in _testContext.Usergroup on user.UserGroup equals myUsergroup.GroupId
// //条件查询
// // where user.UserId>60150 && user.UserId<
// select new
// {
// user.UserId,
// user.CreateTime,
// user.UserGroup,
// user.UserNo,
// user.UserName,
// myname = myUsergroup.GroupName
// }).ToList();
//return result;
//left Join+分页
//var result = (from user in _testContext.User
// join myUsergroup in _testContext.Usergroup on user.UserGroup equals myUsergroup.GroupId into ud
// from a in ud.DefaultIfEmpty()
// orderby user.UserId
// where (user.UserId>60150 && user.UserId<70150)
// select new
// {
// user.UserId,
// user.CreateTime,
// user.UserGroup,
// user.UserNo,
// user.UserName,
// a.GroupName
// }).Skip(1000).Take(10).ToList();
//sw.Stop();
//ViewBag.spanTime = sw.Elapsed.TotalSeconds;
//ViewBag.dataCount = result.Count;
//return result;
//group by
var result = (from user in _testContext.User
group user by user.UserGroup
into g
select new
{
g.Key,
total = g.Count()
}).ToList();
sw.Stop();
ViewBag.spanTime = sw.Elapsed.TotalSeconds;
ViewBag.dataCount = result.Count;
return result;
}
#endregion