C# EF

EF批量，参数：

https://www.cnblogs.com/shanshanlaichi/p/6666074.html

https://www.cnblogs.com/seanchang/p/9187619.html

 #region 16-批量删除
    /// <summary>
    /// 16-批量删除
    /// </summary>
    /// <typeparam name="T">实体类型</typeparam>
    /// <param name="delWhere">删除条件</param>
    /// <returns></returns>
    public async Task<int> BatchDeleteAsync<T>(Expression<Func<T, bool>> delWhere) where T : class
    {
        int count = await db.Set<T>().Where(delWhere).ExecuteDeleteAsync();
        return count;
    }
    #endregion

    #region 17-批量更新
    /// <summary>
    /// 17-批量更新
    /// </summary>
    /// <typeparam name="T">实体类型</typeparam>
    /// <param name="updateWhere">更新条件</param>
    /// <param name="setPropertyCalls">更新实体表达式</param>
    /// <returns></returns>
    public async Task<int> BatchUpdateAsync<T>(Expression<Func<T, bool>> updateWhere, Expression<Func<SetPropertyCalls<T>, SetPropertyCalls<T>>> setPropertyCalls) where T : class
    {
        int count = await db.Set<T>().Where(updateWhere).ExecuteUpdateAsync(setPropertyCalls);
        return count;
    }
    #endregion

 

    #region  01-批量插入
    /// <summary>
    /// 01-批量插入
    /// </summary>
    /// <typeparam name="T">实体类型</typeparam>
    /// <param name="list">实体集合</param>
    /// <returns></returns>
    public async Task InsertBulkAsync<T>(List<T> list) where T : class
    {
        await db.BulkInsertAsync(list);  
    }
    #endregion

 

            #region 01-批量更新
            {

                int count = await baseService.BatchUpdateAsync<T_SysErrorLog>(u => u.addTime < DateTime.Now,
                    u => u.SetProperty(u => u.delFlag, 1)
                           .SetProperty(u => u.userAccount, u => u.userAccount + "00000")
                );

            }
            #endregion



            #region 02-批量删除 
            {
                int count = await baseService.BatchDeleteAsync<T_SysErrorLog>(u => u.delFlag == 1);
            }
            #endregion

 

EF增删改查
参考：
https://www.cnblogs.com/zry2510/p/6209118.html

EF查询表的某个字段的最大值
var a=db.表名.Select(s=>s.列名).Max();

EF查询表是否表中已存在某个值
var a=db.表名.Any(s=>s.列名==传入的值);

if(a){ 已存在 }

或者

from x in a where !b.Any(y=>y.id==x.id) select x;

EF 查询所有字段
var query=db.表名.Where(r=> r.Id==Id).Select(p=>p).ToList();

EF 查询部分字段
var query=db.表名.Where(r=> r.Id==Id).Select(g=>new{d.Id, d.想要的字段}).ToList();

EF修改部分字段
参考：
https://www.cnblogs.com/jhxk/articles/9719606.html
https://www.cnblogs.com/zxsn/p/12658355.html

EF 链表查询
参考：
https://www.cnblogs.com/tinya/p/4623503.html
https://www.cnblogs.com/renyan52099/p/14781372.html
http://www.voidcn.com/article/p-rqfusmvr-bqh.html

查看EF生成的SQL语句
参考：
https://www.cnblogs.com/cxxtreasure/p/13382726.html

EF执行Sql查询
参考：
https://www.cnblogs.com/cxxtreasure/p/13382695.html

EF + Lambda分页
参考：
https://blog.csdn.net/xoofly/article/details/84317408

EF + LINQ查询前N条记录
参考：
https://blog.csdn.net/ptyzhu/article/details/7893563

linq GroupBy 多字段分组

参考：

https://www.cnblogs.com/tianyang1027/p/13931811.html

 

C＃EF保存多个记录

using(var db = context)
{
  var dataToUpdate = db.Employees.ToList();

   var department= "IT";

   dataToUpdate.ForEach(x=>{
       x.department = department;
   });

   db.SaveChanges();
}

　　

 比较EF的Lambda查询和Linq查询写法的区别

https://www.cnblogs.com/yaopengfei/p/7678755.html

结合EF的本地缓存属性来介绍【EF增删改操作】的几种形式

https://www.cnblogs.com/yaopengfei/p/7674715.html

本地缓存、立即加载、延迟加载(不含导航属性)

https://www.cnblogs.com/yaopengfei/p/7701481.html

EF的三种事务的应用场景和各自注意的问题(SaveChanges、DBContextTransaction、TransactionScope)

https://www.cnblogs.com/yaopengfei/p/7748221.html

泛型（泛型类、接口、方法、委托、泛型约束、泛型缓存、逆变和协变）

https://www.cnblogs.com/yaopengfei/p/6880629.html