目录
一.EF修改和删除的多种方法
二.标准查询where
三.include
四.skip take
五.反射获取实例属性
六.EF DLL数据访问帮助类
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
1 var student = db.Students.FirstOrDefault(t => t.Id == Mid);
2 student.Name = "修改后";//修改值数据
3 db.SaveChanges();//保存
4 db.Students.Remove(student);//移除对象
5 db.SaveChanges();//保存
方法2：先附加到ef实体对象 然后在移除
1 Students s = new Students();
2 s.Id = int.Parse(id);
3 db.Students.Attach(s);//将实体附加到 上下文中 ；
4 db.Students.Remove(s);
5 if (db.SaveChanges() >= 1)
6 {
7 //成功
8 }
方法3：添加到ef实体对象 然后标记删除
1 Students s = new Students();
2 s.Id = int.Parse(id);
3 db.Entry<Students>(s).State = System.Data.EntityState.Deleted;//标记删除
4 int num = db.SaveChanges();
方法4：修改实体
1 //这里需要关闭验证 不然会报错
2 db.Configuration.ValidateOnSaveEnabled = false;
3 DbEntityEntry dbS = db.Entry<Students>(s);
4 dbS.State = System.Data.EntityState.Unchanged; //清楚所有字段标记
5 dbS.Property("Gender").IsModified = true;//标记修改字段
6 int num = db.SaveChanges();
7 db.Configuration.ValidateOnSaveEnabled = true;//打开验证
8 if (num >= 1)
9 {
10 //修改成功
11 }
二.标准查询where 在不同场景 实现方法不一样
1 //场景1：ef的数据集 使用where 是在 IQueryable 的扩展方法
2 //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 //1.自动 连接查询【无Include】
2 var stu1 = db.Students.Where(t => t.Classes.CName == "zha");
3 var cname = stu1.FirstOrDefault();
1 SELECT TOP (1)
2 [Extent1].[Id] AS [Id],
3 [Extent1].[CId] AS [CId],
4 [Extent1].[Name] AS [Name],
5 [Extent1].[Gender] AS [Gender],
6 [Extent1].[IsDel] AS [IsDel],
7 [Extent1].[AddTime] AS [AddTime]
8 FROM [dbo].[Students] AS [Extent1]
9 INNER JOIN [dbo].[Classes] AS [Extent2] ON [Extent1].[CId] = [Extent2].[CID]
10 WHERE 'zha' = [Extent2].[CName]
场景2：手动 内连接查询【有Include】
1 //2手动 内连接查询【有Include】
2 var stu2 = db.Students.Include("Classes").Where(t => t.Id == 11);
3 var ccc = stu2.FirstOrDefault().Classes.CName;
1 SELECT
2 [Limit1].[Id] AS [Id],
3 [Limit1].[CId] AS [CId],
4 [Limit1].[Name] AS [Name],
5 [Limit1].[Gender] AS [Gender],
6 [Limit1].[IsDel] AS [IsDel],
7 [Limit1].[AddTime] AS [AddTime],
8 [Extent2].[CID] AS [CId1],
9 [Extent2].[CName] AS [CName],
10 [Extent2].[CCount] AS [CCount],
11 [Extent2].[CImg] AS [CImg],
12 [Extent2].[CIsDel] AS [CIsDel],
13 [Extent2].[CAddTime] AS [CAddTime]
14 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]
15 FROM [dbo].[Students] AS [Extent1]
16 WHERE 11 = [Extent1].[Id] ) AS [Limit1]
17 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】
1 //3.无连接查询 分两次sql查询【无Include】
2 var stucc = db.Students.Where(t => t.Id == 11);
3 var zz = stucc.FirstOrDefault().Classes.CName;
1 SELECT TOP (1)
2 [Extent1].[Id] AS [Id],
3 [Extent1].[CId] AS [CId],
4 [Extent1].[Name] AS [Name],
5 [Extent1].[Gender] AS [Gender],
6 [Extent1].[IsDel] AS [IsDel],
7 [Extent1].[AddTime] AS [AddTime]
8 FROM [dbo].[Students] AS [Extent1]
9 WHERE 11 = [Extent1].[Id];
10
11 SELECT
12 [Extent1].[CID] AS [CID],
13 [Extent1].[CName] AS [CName],
14 [Extent1].[CCount] AS [CCount],
15 [Extent1].[CImg] AS [CImg],
16 [Extent1].[CIsDel] AS [CIsDel],
17 [Extent1].[CAddTime] AS [CAddTime]
18 FROM [dbo].[Classes] AS [Extent1]
19 WHERE [Extent1].[CID] = @EntityKeyValue1
四.skip take
1 //Skip 跳过序列中指定数量的元素，然后返回剩余的元素。
2 //Take 从序列的开头返回指定数量的连续元素。
3 //根据这两个方法可以 实现 分页效果
五.反射获取实例属性
1 //利用反射 获取 类 对象 的所有公共 属性 默认是[GetProperties(BindingFlags.Instance | BindingFlags.Public)]
2 var listPro = typeof(Students).GetProperties().ToList();
3 object obj1 = new object();
4 object obj2 = new object();
5 listPro.ForEach(l =>
6 {
7 var newValue = l.GetValue(obj1); //获得某个对象的属性值
8 l.SetValue(obj2, newValue);//修改一个对象的属性 值
9 });
六.EF DLL数据访问帮助 父类
1 using _00EFModel;
2 using System;
3 using System.Collections.Generic;
4 using System.Linq;
5 using System.Linq.Expressions;
6 using System.Reflection;
7 using System.Text;
8 using System.Threading.Tasks;
9
10 namespace _00EFDLL
11 {
12 /// <summary>
13 /// 数据访问 父类
14 /// </summary>
15 public class BaseDLL<Tclass> where Tclass : class,new()
16 {
17 /// <summary>
18 /// 数据访问上下文
19 /// </summary>
20 _00EFModel.Entities db = new _00EFModel.Entities();
21
22 #region 1.0添加数据 + Add(Tclass model)
23 /// <summary>
24 /// 1.0添加数据
25 /// </summary>
26 /// <param name="model"></param>
27 public void Add(Tclass model)
28 {
29 db.Set<Tclass>().Add(model);
30 }
31 #endregion
32
33 #region 2.0 删除方法1 删除给定的对象 +Del(Tclass model)
34 /// <summary>
35 /// 2.0 删除方法1 删除给定的对象
36 /// </summary>
37 /// <param name="model"></param>
38 public void Del(Tclass model)
39 {
40 //将实体 添加到上下文
41 db.Set<Tclass>().Attach(model);
42 //把实体 标记为删除
43 db.Set<Tclass>().Remove(model);
44 }
45 #endregion
46
47 #region 2.1 删除方法2 根据条件删除对象 +Del(Expression<Func<Tclass, bool>> delWhere)
48 /// <summary>
49 /// 2.1 删除方法2 根据条件删除对象
50 /// </summary>
51 /// <param name="delWhere"></param>
52 public void Del(Expression<Func<Tclass, bool>> delWhere)
53 {
54 //查询所有满足条件的实体对象
55 var modelS = db.Set<Tclass>().Where(delWhere).ToList();
56 modelS.ForEach(m =>
57 {
58 //附加到 上下文
59 db.Set<Tclass>().Attach(m);
60 //标记为 删除状态
61 db.Set<Tclass>().Remove(m);
62 });
63 }
64 #endregion
65
66 #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)
67 /// <summary>
68 /// 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】
69 /// </summary>
70 /// <param name="model"></param>
71 /// <param name="strparams">可变参数</param>
72 public int Up(Tclass model, params string[] strparams)
73 {
74 //关闭检查
75 db.Configuration.ValidateOnSaveEnabled = false;
76 //附加到上下文
77 var m = db.Entry<Tclass>(model);
78 //把全部属性标记为 没有修改
79 m.State = System.Data.Entity.EntityState.Unchanged;
80 for (int i = 0; i < strparams.Length; i++)
81 {
82 //标记要修改的属性
83 m.Property(strparams[i]).IsModified = true;
84 }
85 int num = db.SaveChanges();
86 //打开检查
87 db.Configuration.ValidateOnSaveEnabled = true;
88 return num;
89 }
90 #endregion
91
92 #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)
93 /// <summary>
94 /// 3.1 修改方法2 根据条件 修改指定的 属性 值
95 /// </summary>
96 /// <param name="upWhere"></param>
97 /// <param name="model"></param>
98 /// <param name="strparame"></param>
99 public void Up(Expression<Func<Tclass, bool>> upWhere, Tclass model, params string[] strparame)
100 {
101 //查询出满足条件的所有实体
102 var modelS = db.Set<Tclass>().Where(upWhere).ToList();
103 //利用反射 获取 类 对象 的所有公共 属性 默认是[GetProperties(BindingFlags.Instance | BindingFlags.Public)]
104 var listPro = typeof(Tclass).GetProperties().ToList();
105 // 属性对象 键值对
106 List<PropertyInfo> dic = new List<PropertyInfo>();
107 listPro.ForEach(l =>
108 {
109 for (int i = 0; i < strparame.Length; i++)
110 {
111 //循环 判断 添加 需要修改的 属性对象
112 if (l.Name == strparame[i].Trim())
113 {
114 dic.Add(l);
115 break;
116 }
117 }
118 });
119
120 if (dic.Count > 0)//判断 属性对象集合 是否 有 数据
121 {
122 foreach (var property in dic)
123 {
124 //取 传过来的对象 里面的值
125 var newValue = property.GetValue(model);
126 foreach (var mymodel in modelS)
127 {
128 //修改到 对象集合
129 property.SetValue(mymodel, newValue);
130 }
131 }
132 }
133 }
134 #endregion
135
136 #region 4.0 查询方法 +GetList<Tkey>(Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
137 /// <summary>
138 /// 4.0 查询方法
139 /// </summary>
140 /// <typeparam name="Tkey"></typeparam>
141 /// <param name="strWhere">查询条件</param>
142 /// <param name="strOrederBy">排序条件</param>
143 /// <param name="order">是否升序</param>
144 /// <returns></returns>
145 public List<Tclass> GetList<Tkey>(Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
146 {
147 var t = db.Set<Tclass>().Where(strWhere);
148 if (strOrederBy != null)
149 {
150 if (order)
151 t = t.OrderBy(strOrederBy);
152 else
153 t = t.OrderByDescending(strOrederBy);
154 }
155 return t.ToList();
156 }
157 #endregion
158
159 #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)
160 /// <summary>
161 /// 4.1 查询方法2 分页查询
162 /// </summary>
163 /// <typeparam name="Tkey"></typeparam>
164 /// <param name="indexPage">页码</param>
165 /// <param name="sizePage">页容量</param>
166 /// <param name="strWhere">查询条件</param>
167 /// <param name="strOrederBy">排序字段</param>
168 /// <param name="order">是否升序</param>
169 /// <returns></returns>
170 public List<Tclass> GetList<Tkey>(int indexPage, int sizePage, Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true)
171 {
172 var t = db.Set<Tclass>().Where(strWhere);
173 if (strOrederBy != null)
174 {
175 if (order)
176 t = t.OrderBy(strOrederBy);
177 else
178 t = t.OrderByDescending(strOrederBy);
179 }
180 return t.Skip((indexPage - 1) * sizePage).Take(sizePage).ToList();
181 }
182 #endregion
183
184 #region 提交 +save()
185 /// <summary>
186 /// 提交
187 /// </summary>
188 /// <returns></returns>
189 public int save()
190 {
191 return db.SaveChanges();
192 }
193 #endregion
194 }
195 }
