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一.EF修改和删除的多种方法
方法1：官方推荐 先查询在修改 或者删除
var student = db.Students.FirstOrDefault(t => t.Id == Mid); student.Name = "修改后";//修改值数据 db.SaveChanges();//保存 db.Students.Remove(student);//移除对象 db.SaveChanges();//保存
方法2：先附加到ef实体对象 然后在移除
Students s = new Students();
s.Id = int.Parse(id);
db.Students.Attach(s);//将实体附加到 上下文中 ；
db.Students.Remove(s);
if (db.SaveChanges() >= 1)
{
//成功
}方法3：添加到ef实体对象 然后标记删除
Students s = new Students(); s.Id = int.Parse(id); db.Entry<Students>(s).State = System.Data.EntityState.Deleted;//标记删除 int num = db.SaveChanges();
方法4：修改实体
//这里需要关闭验证 不然会报错
db.Configuration.ValidateOnSaveEnabled = false;
DbEntityEntry dbS = db.Entry<Students>(s);
dbS.State = System.Data.EntityState.Unchanged; //清楚所有字段标记
dbS.Property("Gender").IsModified = true;//标记修改字段
int num = db.SaveChanges();
db.Configuration.ValidateOnSaveEnabled = true;//打开验证
if (num >= 1)
{
//修改成功
}二.标准查询where 在不同场景 实现方法不一样
//场景1：ef的数据集 使用where 是在 IQueryable 的扩展方法 //场景2：List集合的数据集 使用where 是在 IEnumerable 的扩展方法
三.include
场景1：自动 连接查询【无Include】
//1.自动 连接查询【无Include】 var stu1 = db.Students.Where(t => t.Classes.CName == "zha"); var cname = stu1.FirstOrDefault(); SELECT TOP (1) [Extent1].[Id] AS [Id], [Extent1].[CId] AS [CId], [Extent1].[Name] AS [Name], [Extent1].[Gender] AS [Gender], [Extent1].[IsDel] AS [IsDel], [Extent1].[AddTime] AS [AddTime] FROM [dbo].[Students] AS [Extent1] INNER JOIN [dbo].[Classes] AS [Extent2] ON [Extent1].[CId] = [Extent2].[CID] WHERE 'zha' = [Extent2].[CName]
场景2：手动 内连接查询【有Include】
//2手动 内连接查询【有Include】
var stu2 = db.Students.Include("Classes").Where(t => t.Id == 11);
var ccc = stu2.FirstOrDefault().Classes.CName;
SELECT
[Limit1].[Id] AS [Id],
[Limit1].[CId] AS [CId],
[Limit1].[Name] AS [Name],
[Limit1].[Gender] AS [Gender],
[Limit1].[IsDel] AS [IsDel],
[Limit1].[AddTime] AS [AddTime],
[Extent2].[CID] AS [CId1],
[Extent2].[CName] AS [CName],
[Extent2].[CCount] AS [CCount],
[Extent2].[CImg] AS [CImg],
[Extent2].[CIsDel] AS [CIsDel],
[Extent2].[CAddTime] AS [CAddTime]
FROM (SELECT TOP (1) [Extent1].[Id] AS [Id], [Extent1].[CId] AS [CId], [Extent1].[Name] AS [Name], [Extent1].[Gender] AS [Gender], [Extent1].[IsDel] AS [IsDel], [Extent1].[AddTime] AS [AddTime]
FROM [dbo].[Students] AS [Extent1]
WHERE 11 = [Extent1].[Id] ) AS [Limit1]
LEFT OUTER JOIN [dbo].[Classes] AS [Extent2] ON [Limit1].[CId] = [Extent2].[CID]场景3：无连接查询 分两次sql查询【无Include】
//3.无连接查询 分两次sql查询【无Include】 var stucc = db.Students.Where(t => t.Id == 11); var zz = stucc.FirstOrDefault().Classes.CName; SELECT TOP (1) [Extent1].[Id] AS [Id], [Extent1].[CId] AS [CId], [Extent1].[Name] AS [Name], [Extent1].[Gender] AS [Gender], [Extent1].[IsDel] AS [IsDel], [Extent1].[AddTime] AS [AddTime] FROM [dbo].[Students] AS [Extent1] WHERE 11 = [Extent1].[Id]; SELECT [Extent1].[CID] AS [CID], [Extent1].[CName] AS [CName], [Extent1].[CCount] AS [CCount], [Extent1].[CImg] AS [CImg], [Extent1].[CIsDel] AS [CIsDel], [Extent1].[CAddTime] AS [CAddTime] FROM [dbo].[Classes] AS [Extent1] WHERE [Extent1].[CID] = @EntityKeyValue1 四.skip take //Skip 跳过序列中指定数量的元素，然后返回剩余的元素。 //Take 从序列的开头返回指定数量的连续
元素。
//根据这两个方法可以 实现 分页效果
五.反射获取实例属性
//利用反射 获取 类 对象 的所有公共 属性 默认是[GetProperties(BindingFlags.Instance | BindingFlags.Public)]
var listPro = typeof(Students).GetProperties().ToList();
object obj1 = new object();
object obj2 = new object();
listPro.ForEach(l =>
{
var newValue = l.GetValue(obj1); //获得某个对象的属性值
l.SetValue(obj2, newValue);//修改一个对象的属性 值
});六.EF DLL数据访问帮助 父类
using _00EFModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
namespace _00EFDLL
{
/// <summary>
/// 数据访问 父类
/// </summary>
public class BaseDLL<Tclass> where Tclass : class,new()
{
/// <summary>
/// 数据访问上下文
/// </summary>
_00EFModel.Entities db = new _00EFModel.Entities();
#region 1.0添加数据 + Add(Tclass model)
/// <summary>
/// 1.0添加数据
/// </summary>
/// <param name="model"></param>
public void Add(Tclass model)
{
db.Set<Tclass>().Add(model);
}
#endregion
#region 2.0 删除方法1 删除给定的对象 +Del(Tclass model)
/// <summary>
/// 2.0 删除方法1 删除给定的对象
/// </summary>
/// <param name="model"></param>
public void Del(Tclass model)
{
//将实体 添加到上下文
db.Set<Tclass>().Attach(model);
//把实体 标记为删除
db.Set<Tclass>().Remove(model);
}
#endregion
#region 2.1 删除方法2 根据条件删除对象 +Del(Expression<Func<Tclass, bool>> delWhere)
/// <summary>
/// 2.1 删除方法2 根据条件删除对象
/// </summary>
/// <param name="delWhere"></param>
public void Del(Expression<Func<Tclass, bool>> delWhere)
{
//查询所有满足条件的实体对象
var modelS = db.Set<Tclass>().Where(delWhere).ToList();
modelS.ForEach(m =>
{
//附加到 上下文
db.Set<Tclass>().Attach(m);
//标记为 删除状态
db.Set<Tclass>().Remove(m);
});
}
#endregion
#region 3.0 修改方法1 修改某个实体的 某些属性 +Up(Tclass model, params string[] strparams)
/// <summary>
/// 3.0 修改方法1 修改某个实体的 某些属性(根据id修改)【*用这个需要注意关闭检查】
/// </summary>
/// <param name="model"></param>
/// <param name="strparams">可变参数</param>
public int Up(Tclass model, params string[] strparams)
{
//关闭检查
db.Configuration.ValidateOnSaveEnabled = false;
//附加到上下文
var m = db.Entry<Tclass>(model);
//把全部属性标记为 没有修改
m.State = System.Data.Entity.EntityState.Unchanged;
for (int i = 0; i < strparams.Length; i++)
{
//标记要修改的属性
m.Property(strparams[i]).IsModified = true;
}
int num = db.SaveChanges();
//打开检查
db.Configuration.ValidateOnSaveEnabled = true;
return num;
}
#endregion
#region 3.1 修改方法2 根据条件 修改指定的 属性 值 +Up(Expression<Func<Tclass, bool>> upWhere, Tclass model, params string[] strparame)
/// <summary>
/// 3.1 修改方法2 根据条件 修改指定的 属性 值
/// </summary>
/// <param name="upWhere"></param>
/// <param name="model"></param>
/// <param name="strparame"></param>
public void Up(Expression<Func<Tclass, bool>> upWhere, Tclass model, params string[] strparame)
{
//查询出满足条件的所有实体
var modelS = db.Set<Tclass>().Where(upWhere).ToList();
//利用反射 获取 类 对象 的所有公共 属性 默认是[GetProperties(BindingFlags.Instance | BindingFlags.Public)]
var listPro = typeof(Tclass).GetProperties().ToList();
// 属性对象 键值对
List<PropertyInfo> dic = new List<PropertyInfo>();
listPro.ForEach(l =>
{
for (int i = 0; i < strparame.Length; i++)
{
//循环 判断 添加 需要修改的 属性对象
if (l.Name == strparame[i].Trim())
{
dic.Add(l);
break;
}
}
});
if (dic.Count > 0)//判断 属性对象集合 是否 有 数据
{
foreach (var property in dic)
{
//取 传过来的对象 里面的值
var newValue = property.GetValue(model);
foreach (var mymodel in modelS)
{
//修改到 对象集合
property.SetValue(mymodel, newValue);
}
}
}
}
#endregion
#region 4.0 查询方法 +GetList<Tkey>(Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
/// <summary>
/// 4.0 查询方法
/// </summary>
/// <typeparam name="Tkey"></typeparam>
/// <param name="strWhere">查询条件</param>
/// <param name="strOrederBy">排序条件</param>
/// <param name="order">是否升序</param>
/// <returns></returns>
public List<Tclass> GetList<Tkey>(Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
{
var t = db.Set<Tclass>().Where(strWhere);
if (strOrederBy != null)
{
if (order)
t = t.OrderBy(strOrederBy);
else
t = t.OrderByDescending(strOrederBy);
}
return t.ToList();
}
#endregion
#region 4.1 查询方法2 分页查询 +GetList<Tkey>(int indexPage, int sizePage, Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
/// <summary>
/// 4.1 查询方法2 分页查询
/// </summary>
/// <typeparam name="Tkey"></typeparam>
/// <param name="indexPage">页码</param>
/// <param name="sizePage">页容量</param>
/// <param name="strWhere">查询条件</param>
/// <param name="strOrederBy">排序字段</param>
/// <param name="order">是否升序</param>
/// <returns></returns>
public List<Tclass> GetList<Tkey>(int indexPage, int sizePage, Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
{
var t = db.Set<Tclass>().Where(strWhere);
if (strOrederBy != null)
{
if (order)
t = t.OrderBy(strOrederBy);
else
t = t.OrderByDescending(strOrederBy);
}
return t.Skip((indexPage - 1) * sizePage).Take(sizePage).ToList();
}
#endregion
#region 提交 +save()
/// <summary>
/// 提交
/// </summary>
/// <returns></returns>
public int save()
{
return db.SaveChanges();
}
#endregion
}
}